CHAPTER 18
Bees,
Wasps and Ants
Hornets, Yellow Jackets, Paper Wasps. Being true social insects, these critters have a
well-developed caste system. In a
typical mature wasp nest there are many workers and one or more kings and
queens. Unlike some of the other social
insects discussed in this CD, there are fewer differences in the appearance of
each caste.
Hornets, yellow jackets
and paper wasps all exhibit the same general life cycle. Their nesting cycle is
annual, with only mated queens surviving the winter in a variety of protected
locations--including under bark and in attics.
In early spring the queen emerges and may reoccupy an old nest, or
construct a new one. Regardless of which
condition prevails, the queen initially deposits a few single eggs-one to each
cell. Upon hatching, the larvae are fed a variety of insect larvae (mainly
caterpillars) that are captured and brought back to the nest by the adult queen
wasp.
The adult wasps feed primarily on nectar, ripe fruit and other
substances that are high in sugar. They
do require a certain amount of protein in their diet which is typically acquired
from the larvae. As adults wasps are
feeding their larvae, the larvae exude a proteinaceous material from their
mouth that is quickly consumed by the adult. The majority of these larvae will
develop into adult workers, which take over the duties of expanding the nest,
collecting food and feeding the young (Figure 18A). The queen continues to lay
more eggs; this results in several generations with the colony continuing to
increase in size into the fall. In the
late fall, new kings and queens are produced, mating occurs, and the newly
mated queens overwinter, completing the annual cycle.
Left. Mating yellow jackets. Right.
Paper wasp.
Some consider these
wasps beneficial, as they are predatory on different pest species. Besides feeding on caterpillars and other
insects and spiders, these insects are attracted to any meat source, a
phenomenon, which is frequently observed much to the displeasure of campers,
clients of or participants in restaurants, snack bars and backyard barbecues
The nests of
hornets, yellow jackets and paper wasps are constructed out of cellulose, which
is collected by the adult workers from a variety of sources, including old
newspapers, cardboard, weathered wood, and bark. Once collected, these materials are chewed,
saliva is added and they are formed into cells basically appearing like those in
honey bee comb.
With paper wasps
the nest is a single layer that is suspended upside down by a short stalk. Around the home, paper wasp nests typically
are found under eaves, along fences, or can be found attached to trees and
plants. Hornet and yellow jacket nests may exist above or below ground; their
nests are much larger than those of paper wasps, and are constructed of many
layers of cells that are surrounded by a capsule-like structure.
Left. A paper wasp nest with a dozen or
so workers. Right. A large hornet
nest. Image courtesy CDC Healthwise
Photo Library-Dr Gary Alpert.
Since paper wasp nest
are single-layered it follows that mature colonies of these insects are much
smaller than those of the multiplayer nests of hornets and yellow jackets. The nest of a paper wasp typically contains a
few dozen adults while the nests of hornets and yellow jackets may number in
the thousands.
Paper wasp colonies
although common under the eaves of houses do not typically pose a threat to the
homeowner unless the nest is disturbed.
If disturbed they will readily defend the nest and sting is similar to
that of a bee although unlike that of a honey bee these insects can sting
repeatedly.
I was once asked in
class how to remove a paper wasp nest from the eves of a home. Although not in the position to recommend
such a task there are sprays available at garden centers that provide an
instant knock down an subsequent kill of wasps and bees. One of the students in the class said she
used hair spray which upon drying prevented the wasps from flying. Another student immediately added that she
uses hair spray but lights it! Both seem quite unacceptable and possibly
dangerous!
The most common
social wasp found in the Western United States is the western yellow
jacket. This species typically nests
underground, but occasionally is found in wall voids and other protected
locations. As with other members of this
group these insects are predatory in nature but when their natural food is
scarce they are attracted to any type of meat or sweets. Certain years these insects become extremely
common and are major pests around campgrounds, restaurants and even backyards. One major factor relating to larger numbers
during certain years is previous mild winters.
Under these conditions the nests may not totally die out during the
winter months.
An official from
Catalina Island recently contacted me.
The yellow jackets had become a major concern over the entire several-mile
long island. In Avalon when customers
ordered a hamburger and a coke at one of the restaurants it was a matter of
whom or what got to the food first. One year on 3 separate occasions children
had to Medi-vaced by helicopter out of the Boy Scout camps due to massive
number of stings from these wasps.
Students frequently
ask me what is the worst sting-bite that I personally have experienced. I have been stung by many scorpions, many
species of ants, exotic caterpillars and hundreds of bees at one time and
bitten by large beetles, giant waterbugs, assassin bugs, various tarantulas and
black widows but the worst encounter was by a colony of yellow jackets. The
sting of a yellow jacket or hornet is considerably worse than that of a honeybee. I was once called to remove a honeybee nest
from a property. When I got there it was
a yellow jacket nest in the ground. Even
though, I was only prepared for honeybees (a veil and hat) I decided to
continue. After about 15 stings (over a
period of 20 minutes) I decided to retreat and get some better protective
clothing. By the time I got back to my
vehicle most of my body had turned bright red with hives and large red welts. Besides
the initial pain I itched for several days. I once received a single sting from
a large hornet in Mexico. The initial
pain was much worse than that of a honeybee and within less than one minute I
had such a severe headache that I could not stand up for several minutes.
Bald Face Hornet-Dolichovespula maculata. This is a North American insect
commonly called the bald-faced hornet (or white-faced hornet or white-tailed hornet). Its well-known features include its hanging
paper nests and the females' habit of defending them with repeated stings.
Bald Face Hornet. Image Courtesy of PiccoloNamek.
It belongs to a genus of wasps called yellow jackets in North
America, but is not called that because it lacks yellow coloring. Instead, it
is called a hornet in the American sense of a wasp that builds paper nests,
especially one of the subfamily Vespinae. It is not a "true hornet" in the British
sense, that is, a member of the genus Vespa in the same
subfamily, such as the Asian giant hornet or the European hornet.
The bald-faced hornet lives throughout North America, including southern Canada, the Rocky
Mountains, the western coast of the United States, and most of the eastern US.
They are most common in the southeastern United States. They are best known for their large football-shaped paper nest, which they build in the spring for raising their
young. These nests can sometimes reach 3 feet tall. Like the median wasp (Dolichovespula
media) in Europe, bald-faced
hornets are extremely protective of their nests and will sting repeatedly if
disturbed.
Every year, queens that were
born and fertilized at the end
of the previous season begin a new colony. The queen selects a location for its
nest, begins building it, lays a first batch of eggs and feeds this first group
of larvae. These become workers and will assume the chore of expanding the nest
— done by chewing up wood which is mixed with a starch in their saliva. This
mixture is then spread with their mandibles and legs,
drying into the paper-like substance that makes up the nest. The workers also
guard the nest and feed on nectar, tree sap
and fruit pulp. They also capture insects and arthropods, which are chewed up to be fed to the larvae. This
continues through summer and into fall. Near the end of summer, or early in the
fall, the queen begins to lay eggs which will become drones and new queens.
After pupation, these fertile males and females will mate, setting up next
year's cycle of growth.
Remains of Bald Faced Hornet Nest.
Image Courtesy of Makuabob.
As winter approaches, the wasps die — except any
just-fertilized queens. These hibernate underground, on hollow trees until
spring or other protected locations. The nest itself is generally abandoned by
winter, and will most likely not be reused. When spring arrives, the young
queens emerge and the cycle begins again.
Bald-faced hornets visit flowers for nectar,
especially in late summer, and can be minor pollinators.
Like other social wasps, bald-faced hornets have a caste system made up, in one nest, of the
following: Queen — the fertile female which starts the colony and lays eggs;
Workers — infertile females which do all work except laying eggs; Drones — males,
which have no stingers, and are born from unfertilized eggs; New queens —
fertile females, each of which, once fertilized, may start its own nest in the
spring.
Bald-face hornets will sting repeatedly if disturbed.
Like other
stinging wasps, they can sting repeatedly because the stinger does not become
stuck in the skin. Some suggest putting baking soda or meat tenderizer on the area
of the sting, but others
say such treatments do not work.
European Hornet-Vespa crabro.
This species is commonly known simply as the "hornet", is the largest European true social wasp. The queen measures
21–1.4 inches long; males and workers are smaller. The antennae have 13
segments, while in females there are only 12
This species is not particularly aggressive except when
defending the nest, and care must be taken when in its proximity, as the stings
are quite painful. As with most stinging insects, European hornets will sting
in self-defense when grabbed or stepped on.
Eyes are deeply indented, shaped like C. Wings are reddish-orange,
the petiolate abdomen is
brown striped with yellow. The European hornet is larger than common wasp, but smaller than some Asian hornet species. It has hair on the thorax and
abdomen, although the European hornet is not so hairy as most bees.
European Hornets. Left Image
Courtesy of Seçkin resimler. Right Image Courtesy of Aconcagua.
European hornets are often mischaracterized as very
aggressive and dangerous, and are greatly feared by some people. Some people
believe that "three stings from the European hornet can kill an adult
human, and that seven can kill a horse". These are common myths - a sting
from a European hornet isn't any more dangerous than any other wasp sting, and
European hornets are less aggressive than other wasps. In contrast, multiple Asian giant hornets stings are, in fact, more dangerous.
While impressive due to their size and loud sound,
European hornets are in fact much less aggressive than some of their smaller
relatives, such as the German wasp and the
common wasp. When approached, European hornets can actually be seen to slowly
crawl backwards and eventually flee, rather than attack. This can make it hard
to remove hornets from indoors, if they happen to come in through an open
window or door. While not aggressive when encountered far from the nest,
multiple workers will vigorously defend the nest if provoked. Nests can be
approached without provocation (by moving slowly and not breathing towards the
nest) to about 20 inches. Nests are usually not a problem outside buildings,
but because they drip feces, a bad smelling black liquid, nests inside sheds or
walls can be a problem.
Unwarranted fear has often led to the destruction of
nests, leading to the decline of the species, which is often locally threatened
or even endangered. European hornets benefit from legal protection in some
countries, notably Germany, where it has been illegal to kill a European hornet
or nest since 1 January 1987, with a fine up to 50,000 Euros.
European hornets are attracted to lights at night, but
are not attracted to human foods and food wastes. However, they can totally
destroy fruits, such as apples, while the fruit is still on the tree. This is
quite unlike the bald-faced hornet or other
social wasps.
The Japanese Hornet. I have
saved this beast for last since it is probably the most frightening of all the
Hymenoptera. As its name implies it
occurs mainly in Japan which is of course good for us since it is a treacherous
and dangerous insect. It is quite large
approaching the size of a thumb and by the way its sting, besides feeling like
a hot nail driven into you, can also dissolve tissues of your thumb, actually
any part of your body-ouch! Well it is
gets worse. The sting-venom also
contains an alarm pheromone that will incite mass attack from nearby
hornets-hopefully not to a human. Unfortunately
in many cases it is us as 40 to 70 people a year in Japan die from attack of
these critters.
A Japanese
Hornet.
As bad as this is for humans it is much
worse for the European honeybee, Apis
mellifera, the most common honeybee found around the world. These wasps will fly many miles looking for
beehives to raid. They can fly as far as
60 miles in a day at 25 miles per hour. A searching hornet may actually follow
a foraging bee back to its hive. Once
finding the hive it attacks giving off the alarm pheromone attracting other
hornet in the vicinity. Ultimately they typically attack in force with a
relatively small but very effective army of 30 or more. You wouldn’t think such a small army would be
that successful since a beehive can have upwards of 80,000 bees. However, one hornet can kill 40 bees a
minute. Unfortunately honeybees possess relatively
small stingers that are of minimal use in penetrating the thick exocutile of
the invading hornets nor do they defend in mass. The hornets descend on the
hive and systematically one by one cut the bees in half. In the interest of
efficiency they typically cut off the defending bees heads. After a few hours the hive contains few if
any adult bees but there are piles of heads, limbs and various other body
parts. At that point the hornets gorge
on the honey and rip the bee larvae (young) and pupae from their cells and
carry them back to their nest to feed to their young.
However all is not totally lost. There is different species of honeybee which
naturally occurs in Japan that has a defensive tactic it uses against these
invaders. When a single hornet in search
a beehive is detected, hundreds of the worker bees gather at the hive entrance
but readily allow the hornet to enter.
Once in the hive the bees immediately surround and totally cover the
hornet with a ball-like mass of up to 500 individuals. They prevent the hornet from moving and begin
to vibrate their wings muscles. This
action produces heat raising the temperature in the center of the mass (where
the hornet occurs) to around 117 F. This
temperature is not lethal to the bees but the hornet cannot tolerate
temperatures above 113 F and subsequently dies.
Of course action prevents the “scout” hornet from releasing its
pheromones which would normally attract other hornets in the vicinity to mass
attack the hive.
In the mountains of Japan where these hornets are
commonly encountered villagers eat them deep fried. Also a number of companies in Europe and
Japan have begun to manufacture diet supplements and energy drinks which
contain synthetic versions of secretions which the larval hornets feed to adults. The product sold as “hornet juice” is said to
greatly enhance human endurance.
Parasitic (Parasitoids) Hymenoptera
There are many families of Hymenoptera
that are parasitic. In strict entomological terms they are referred to as
parasitoids. In the world of bugs
parasite refers to an insect or one of its relatives (e.g. mites) that feeds on
a host from a different groups animals (e.g. humans) but does not generally
kill it in doing so. Example of this
would include fleas, mites, lice and many others. A parasitoid is an insect or relative that
typically lays its egg or eggs on or in its host which typically belong to the
same group or animals (e.g. insect laying its eggs on another insect). Once the eggs hatch the larvae feed and
develop internally or externally on that host and in doing so kill it.
Thread
Waisted Wasps. As a
group most thread waisted wasps are characterized by an elongated waist or
petiole that joins the thorax to the abdomen. These are commonly found around
the home. However some species have a
narrow waist. In this case they can be separated
from Vespidae by the front wing not bring folded longitudinally. These wasps
can easily be distinguished from other similarly appearing wasps by the
elongated stalk or petiole that connects the thorax to the abdomen; hence
another common name is the thread-waisted wasps. The black and yellow mud dauber, Even though
these are solitary insects a single nest may be composed of several elongated
cylindrical cells made of mud and placed side by side until the make a mass
about the size of a fist. The entire
structure is then plastered over to make a smooth and even outer surface. Each inner cell is provided with several
insect larvae or paralyzed spiders that the adult female has collected. A single egg is then deposited in each cell
and the hatching wasp larvae complete their development on the provided
prey. These wasps are much less
aggressive than solitary forms, as they do not protect their nest. About the only way someone could be stung by
one of these wasps is by accidentally stepping on or carelessly handling one,
which seem very unlikely.
Black
and Yellow Mud Dauber- Sceliphron caementarium. This is solitary insects that
build nests out of mud in sheltered locations, frequently on man-made
structures such as bridges, barns, open porches or under the eaves of houses.
These nests are not aggressively defended, and stings are rare.
Black
and Yellow Mud Dauber.
The black and yellow mud dauber's nest
comprises a series of cylindrical cells that are plastered over to form a
smooth nest that may attain nearly the size of a human fist. After building a
cell, the female wasp captures several spiders.
The captured prey are stung and paralyzed before being placed in the nest, and
then a single egg is deposited on the prey within each cell. The wasp then
seals the cell with mud. After finishing a series of cells, she leaves and does
not return. Eventually, the hatching larva will
eat the prey and emerge from the nest. A common species of cuckoo wasp, Chrysis angolensis, is
frequently a cleptoparasite (steals they prey by laying its eggs
on it)in Sceliphron nests,
and is only one of many different insects that parasitize these mud daubers.
There are some 30 other species of Sceliphron that occur throughout the world,
though in appearance and habits they are quite similar to S. caementarium. S. caementarium is widespread in Canada,
the United States, Central
America, South Africa and the West
Indies, and has been introduced to many Pacific
Islands (including Australia, Hawaii andJapan), Peru and Europe [2],
where it has become established in the western Mediterranean Basin.
It was speculated that a black and yellow
mud dauber built a nest in one of the two tubes of
a Birgenair Boeing
757-200, resulting in the crash of
the airplane.
Organ Pipe Mud Dauber-Trypoxylon politum.
These are fairly large wasps, shiny black with pale hind tarsi.
Male organ pipe mud daubers are among the few male wasps of any species to stay
at the nest. A male "stands guard" (to prevent theft of prey or nest
materials, as well as to ward off parasites while a female is away
collecting spiders.
Mating typically occurs on her visits to the nest. They typically build their
nests in sheltered locations, and large aggregations may form with dozens to
hundreds of nests in a small area. The
shape of their nest is the derivation of their common name.
Organ Pipe Mud Dauber, Nests and
Parasitized Spiders M0ved from Nest. Images Courtesy or Pollinator.
Organ pipe mud
daubers are
also an exceedingly docile species of wasp, and generally pleasant to have
around, as they serve to keep spider populations down. Stings to humans are
very rare, bordering on non-existent, although if squeezed, they will sting in
self-defense. There are a great many other species in the genus Trypoxylon (over 700 of them worldwide), mostly
smaller in size and less abundant.
Sphecius
speciosus-Cicada Killer.
Cicada killer wasps are large, solitary wasps.
The name may be applied to any species which uses cicadas as
prey, though in North America it
is typically applied to a single species, Sphecius speciosus, often simply referred to as "The
cicada killer". However, since there are multiple species of related
wasps, it is more appropriate to call it the Eastern pr Western cicada killers.
These species occurs in the eastern, western and Midwest U.S. and southwards
into Mexico and Central
America. They are so named because they hunt cicadas
and provision their nests with them. In North America they
are sometimes called sand hornets, although they are not hornets,
which belong to the family Vespidae.
Cicada Killer.
Adult Eastern and Western cicada killer
wasps are large, 1.5 to 5 cm (2/3 to 2 inches) long, robust wasps with
hairy, reddish and black areas on the thorax (middle
part), and are black to reddish brown marked with light yellow stripes on the
abdominal (rear) segments. The wings are brownish. Coloration may superficially
resemble that of yellow jackets or hornets.
The females are somewhat larger than the males, and both are among the largest
wasps seen in the Eastern United States, their unusual size giving them a
uniquely fearsome appearance. European hornets (Vespa crabro)
are often mistaken for Eastern cicada killers.
Solitary wasps (such as the Eastern cicada
killer) are very different in their behavior from the social wasps such as hornets, yellow
jackets, and paper
wasps. Cicada killer females use their sting to
paralyze their prey (cicadas)
rather than to defend their nests. Adults feed on flower nectar
and other plant sap exudates.
Adults emerge in summer, typically beginning around late June or early July and
continuing throughout the summer months. They are present in a given area for
60 to 75 days, until mid-September. The large females are commonly seen in
mid-to-late summer skimming around lawns seeking good sites to dig burrows and
searching shrubs and trees for cicadas.
The males are more often seen in groups,
vigorously challenging one another for position on the breeding aggregation
from which they emerged, and generally pursuing anything that moves or flies
within close proximity. It is not unusual to see two or three male wasps locked
together in midair combat, the aggregate adopting an erratic and uncontrolled
flight path until one of the wasps breaks away. The male wasp's aggressive
behavior is extremely similar to that of another robust insect of the area, the
male carpenter bee.
In both cases, while the males' vigorous territorial defense can be extremely
frightening and intimidating to human passersby, the males pose no danger
whatsoever. They will only grapple with other insects, and cannot sting.
This ground-burrowing wasp may be found in
well-drained, sandy soils to loose clay in bare or grass-covered banks, berms
and hills as well as next to raised sidewalks, driveways and patio slabs.
Females may share a burrow, digging their own nest cells off the main tunnel. A
burrow is 15 to 25 cm (6 - 10 in.) deep and about 3 cm
(1.5 in.) wide. The female dislodges the soil with her jaws and pushes
loose soil behind her as she backs out of the burrow using her hind legs, which
are equipped with special spines that help her push the dirt behind her. The
excess soil pushed out of the burrow forms a mound with a trench through it at
the burrow entrance. Cicada killers may nest in planters, window boxes, and
flower beds or under shrubs, ground cover, etc. Nests often are made in the
full sun where vegetation is sparse.
Nest
of Cicada Killer. Image Courtesy of Chuck Holliday.
After digging a nest chamber in the
burrow, female cicada killers capture cicadas, paralyzing them with a sting;
the cicadas then serve as food to rear their young. After paralyzing a cicada,
the female wasp straddles it and takes off toward her burrow; this return
flight to the burrow is difficult for the wasp because the cicada is often more
than twice her weight. After putting the cicada in the nest cell, the female
deposits an egg on the cicada and closes the cell with dirt. Male eggs are laid
on a single cicada but female eggs are given two or sometimes three cicadas;
this is because the female wasp is twice as large as the male and must have
more food. New nest cells are dug as necessary off the main burrow tunnel and a
single burrow may eventually have 10 to 20 cells. The egg hatches in one or two
days, and the cicadas serve as food for the grub. The larvae complete
their development in about 2 weeks. Overwintering occurs as a mature larva within
an earth-coated cocoon. Pupation occurs in the
nest cell in the spring and lasts 25 to 30 days. There is only one generation
per year and no adults overwinter.
Although cicada killers are large, female
cicada killer wasps are not aggressive and rarely sting unless they are grasped
roughly, stepped upon with bare feet, or caught in clothing, etc. One author
who has been stung indicates that, for him, the stings are not much more than a
"pinprick". Males aggressively defend their perching areas on nesting
sites against rival males but they have no sting. Although they appear to
attack anything which moves near their territories, male cicada killers are
actually investigating anything which might be a female cicada killer ready to
mate. Such close inspection appears to many people to be an attack, but male
and female cicada killers don't land on people and attempt to sting. If handled
roughly females will sting, and males will jab with a sharp spine on the tip of
their abdomen. Both sexes are well equipped to bite, as they have large jaws;
however, they don't appear to grasp human skin and bite. They are
non-aggressive towards humans and usually fly away when swatted at, instead of
attacking. Cicada killers exert a natural control on cicada populations and
thus may directly benefit the deciduous trees upon which their cicada prey
feeds.
Chrysisid Wasps.
These tiny wasps are characterized by their shining coloration made
of iridescent blue, green, purple which are true pigments (red, brown and
white) and are very rare in insects. The typical brilliance is emphasized by
the exoskeleton sculpture, which is carved by a complex punctuation and by
projections, crests and holes. In addition there is a reduction of the number
of the external abdominal segments, the presence of 11 antennal segments and
for the wing veins with 5 closed cells. Some tropical species have apterous
females and a body without metallic reflections.
Cuckoo Wasps. Images Courtsey of (left) Pollinator and
(right) Alvesgaspar.
Currently about 3,000
species have been described worldwide. Chrysidids are parasitoids
with some species being cleptoparasites
meaning they lay their eggs on host that are already parasitized by other
wasps. In addition it is not uncommon for the newly hatched cleptoparasitic
larvae to attack and kill the other parasitic larvae thus leaving more food for
themselves
Velvet
Ants. Their common
name velvet ants refers
to their dense hair which may be red, black, white, silver, or gold. They are
known for their extremely painful sting, facetiously said to be strong enough
to kill a cow,
hence the common name cow killer or cow ant.
They invade the nests of wasps and bees as
their exoskeleton is very tough
and roughly textured to protect against stings. Like related families in the Vespoidea,
males have wings but females are wingless. They exhibit extreme sexual
dimorphism; the males and females are so different
that it is almost impossible to associate the two sexes of a species unless
they are captured while mating. In a few species the male is so much larger
than the female that he carries her aloft while mating, a characteristic that
is also seen in the closely related family Tiphiidae. In all Hymenoptera only
the females sting because the stinger is a modified ovipositor.
Like all wasps they can sting multiple times. A structure called a stridulitrum on
the metasoma is
used to produce a squeaking, chirping, or humming warning sound when handled.
Female
(left) and Winged Male Velvet Ants.
Mature velvet ants feed on nectar.
Although most species are strictly nocturnal, females some species are
sometimes active up to two hours before sunset. It is thought they may not
avoid light but rather are active during temperatures which usually occur only
after sunset but on cool overcast days could occur earlier.
The male locates a female on the wing and
mates. The female then enters an insect nest, typically a ground-nesting bee or
wasp nest, and deposits eggs near the larvae or pupae.
Her young develops as an ectoparasitoid,
eventually killing and eating its immobile host. A few European species
have been known to invade and raid bee or wasp nests.
Velvet ants occur worldwide, with some
5000 species, mainly in the tropics.
They are especially common in desert and sandy areas,
with most of the over 400 North American species
found in the Southwestern United States and
adjacent parts of Mexico,
with others found in generally sandy regions throughout the United States and Canada;
the same habitat where their hosts are most diverse.
Spider
Wasps. These are one of the better know groups of
large Hymenoptera. Most
of the Spider Warps are orange and black, black and grey/white markings or just
black, i.e., the very strong warning colors. They usually have tinted wings,
smooth and shiny body. Their hind-legs
are long and always have two prominent spurs. They tend to coil their antennae. Spider wasps are
best distinguished from other similar wasps in
having (in most species) a transverse groove dividing the mesopleuron (the
mesepisternal sclerite, a region on the side of middle segment of the thorax
above the point where the legs join) into halves.
Spider
Wasp with Coiled Antennae and Mesoplural Transverse Groove Dividing Segment
above Attachment of Second Pair of Legs
In South America
spider wasp species may be referred to colloquially as marabunta or marimbondo, though these names can be generally applied to any
very large stinging wasps). The family is cosmopolitan,
with some 4,200 species in 4 subfamilies. All species are solitary, and most
capture and paralyze prey, although some species are cleptoparasites of
other pompilids, or ectoparasitoids of
living spiders. Sexual dimorphism is not marked although females are often
larger than the males.
Spider wasps are long-legged, solitary
wasps that use a single spider as a host for feeding their larvae.
They paralyze the spider with a venomous stinger. Once paralyzed, the spider
is dragged to where a nest will be built – some wasps having already made a
nest. A single egg is laid on the abdomen of the spider, and the nest – or
burrow – is closed.
Spider Wasps Collecting Prey.
Images Courtewy Tony Willis.
The size of the host can influence whether
the wasp will lay an egg that will develop as a male, or an egg that will
develop into a female – larger prey yielding the (larger) females. A
complex set of adult behavior can then occur, such as spreading dirt or
inspecting the area, leaving the nest site inconspicuous. When the wasp larva
hatches it begins to feed on the still-living spider. After consuming the
edible parts of the spider, the larva spins a silk cocoon and pupates –
usually emerging as an adult the next summer. Some species lay the egg on a
still-active spider, where it feeds externally on hemolymph
(spider blood). In time, that spider will die, and the mature wasp larva will
then pupate.
They usually hunt on ground
with the characteristic wing flicking movement. The tarantula hawk is
only one of a number of related species of wasps that mainly parasitize spiders
and in entomological terms are referred to as parasitoids. They typically hunt out their prey, sting and
paralyzed them and carry them back to their nest. The nest is typically a hole in the ground
into which they insert one or more spiders upon which they subsequently lay a
single egg. After hatching the wasp
larva feed on the paralyzed prey until completing development.
Tarantula Hawk-Pepsis spp. This is
a species of spider wasp which
hunts tarantulas as
food for it larvae.
Up to two inches long with a blue-black body and bright rust-colored wings,
tarantula hawks are among the largest of wasps. The coloring on their wings
warns potential predators that they are dangerous (Aposematism). Their long legs have
hooked claws for grappling with their victims. The stinger of a female
tarantula hawk can be up to 1/3 inch long, and delivers a sting which is rated
among the most painful in the insect world.
During the spiders’ reproductive season
male tarantulas are usually emaciated from ignoring food while
searching for females. The tarantula hawks thus prefer female tarantulas and
seek them in their burrows. The females
capture, sting, and paralyze the spider,
Then they either drag the spider back
into her own burrow or transport their prey to a specially prepared nest where
a single egg is
deposited on the spider’s
body, and the entrance is covered. The wasp larva, upon hatching, begins to
suck the juices from the still-living spider.
After the larva grows
a bit, it plunges into the spider's
body and feeds voraciously, avoiding vital organs for
as long as possible to keep it fresh. After completing pupation the adult wasp
emerges from the nest. Tarantula wasps feed primarily on nectar and other
natural sugary materials. The consumption of fermented fruit sometimes
intoxicates them to the point that flight becomes difficult. While the wasps
tend to be most active in daytime summer months, they avoid the very highest temperatures.
The male tarantula hawk does not hunt; instead, it feeds off the flowers of milkweeds,
western soapberry trees,
or mesquite trees.
The male tarantula hawk has a behavior called "hill-topping",
where he sits atop tall plants and watches for females that are ready to
reproduce.
Tarantula
Hawk Dragging Prey to Nest and Feeding on Milkweed Nectar. Image Courtesy of Astrobradley (left) and Davehood
(right).
The tarantula hawk is relatively docile
and rarely stings without provocation. The sting, particularly of Pepsis formosa,
is among the most painful of any insect, but the intense pain only lasts for
about 3 minutes.[ Commenting on his own experience, one researcher
described the pain as "…immediate, excruciating pain that simply shuts
down one's ability to do anything, except, perhaps, scream. Mental discipline
simply does not work in these situations”. In
terms of scale, the wasp's sting is rated near the top of the Schmidt Sting Pain Index,
second only to that of the bullet ant and
is described by Schmidt as "blinding, fierce [and] shockingly
electric". Because of their
extremely large stingers, very few animals are able
to eat them; one of the few animals that can is the roadrunner.
The U.S. State of New
Mexico chose
the insect in 1989 to become its official state insect. The selection of the
insect was prompted by a group of Edgewood, New Mexico,
elementary school children doing research on states which had adopted state
insects. They selected three insects as candidates, and mailed ballots to all
schools for a state wide election. The winner was the Tarantula Hawk Wasp
(specifically, Pepsis formosa).
The RQ-16 T-Hawk unmanned
aerial vehicle has been named after the Tarantula Hawk.
Gall Wasps-Cynipidae. These tiny
wasps are also called gallflies with about 1300 species
worldwide. As indicated they are generally very small creature (1-8
millimeters).
The reproduction of the gall wasp is partly pure
two-sex propagation and partly pure parthenogenesis, in which a male is completely unnecessary. With most
species, however, there is an alternation of generations with one two-sex generation and one
parthenogenic generation annually.
The plant galls mostly develop directly after the
female insect lays the eggs. The reason for gall formation is largely unknown
but is a result of the present of the developing gall insect; it is speculated
that chemical, mechanical and viruses triggers the process. The hatching larvae
feed within the tissue of the galls and are also well-protected from external
environmental effects. The host plants and the size and shape of the galls are
specific to the majority of gall wasps with about 70% of the known species
living in various types of oak trees. Galls
occur on nearly all parts of trees including leaves, buds, branches, and roots. Other
species of plant where galls are commonly found include eucalyptus, rose or maple trees, as well as
many herbs. Frequently, identification a of species of gall forming insect is
easier by the shape of the galls produced rather than the insect itself. Some of the more common types of galls caused
by the feeding of these insects are discussed below.
Oak artichoke galls develop as a
chemically induced distortion of leaf axillary or terminal buds on Pedunculate Oak (Quercus
robur) or Sessile Oak (Quercus petraea) trees, caused by the parthenogenetic gall wasp Andricus fecundatrix which lays single eggs within leaf buds using their ovipositor. The larva
lives inside a smaller hard casing inside the artichoke and this is released in
autumn.
Oak Artichoke Galls. Image Courtesy Rasbak
The galls of the rose gall wasp (Diplolepis
rosae) are also distinctive and are known as bedeguars or robin's
pincushions. These are found on the shoots of dog roses and have a length of up
to five centimeters with red long-haired outgrowths. Inside the galls are
several chambers, which may be occupied by larvae.
Robin’s Pincushion on Rose. Image Courtesy of Bjorn Appel
Knopper galls develop as a
chemically induced distortion of growing acorns on Pedunculate Oak (Quercus robur (L.)) trees,
caused by gall wasps which lay eggs within buds using their ovipositor. The gall thus produced can greatly reduce the fecundity of the oak host, making the gall a potentially more
serious threat than those which develop upon leaves, buds, and stems. The large
one inch gall growth appears as a mass of green to yellowish-green, ridged, and
at first sticky plant tissue on the bud of the oak, that breaks out as the gall
between the cup and the acorn. If only a few grubs are developing within, then
it may appear only as a group of bland folds. Where several grubs are competing
for space the shape may become much more contorted, with several tightly
bunched galls.
Kopper
Galls. Image Courtesy of saharadesertfox.
Neuroterus numismalis is a gall wasp that forms chemically induced leaf galls on oak trees. It has both bisexual and agamic (parthenogenetic)
generations and forms two distinct galls on oak leaves, the Silk button gall and Blister gall. The galls
can be very numerous with more than a thousand per leaf. his Silk button
spangle gall has a cover of golden hairs that give the impression of silk
thread. The 0.3 cm button-shaped galls have a pronounced concavity and sit
tightly against the leaf lamina.
Silk Button Galls on Oak. Image
Courtesy of Image Courtesy of Beentree.
Neuroterus
albipes is a gall wasp that forms
chemically induced leaf galls on oak trees which has both bisexual and
agamic generations and therefore forms two distinct galls, the Smooth Spangle gall and Schenck's gall. The normally cream colored saucer of the
Smooth Spangle gall has a small cone elevated in its centre, a pronounced rim
and they are sometimes found almost folded in two. The gall may have steaks of purple,
red or other colors through it. Typically found on the lower surface, this gall
is found more often on the upper surface than other spangle galls and although
often grouped together, the numbers on each leaf are far fewer than in species
such as Neuroterus quercusbaccarum. The gall is observed to swell
appreciably once it has detached and fallen in late autumn. The gall has also been recorded as
green, purple, red or pink.
Smooth Spangle Gall. Image Courtesy of Rosser1954
BEES
All bees collect nectar and pollen as their main
source of food. One of the
distinguishing characteristics of all these families is that their body hairs
are profusely branched. This adaptation
serves to capture and carry pollen. Worldwide, there are an estimated 20,000
species of bees (Michener, 2000), with approximately 4,000 species native to
the United State. The non-native European honey bee (Apis mellifera) is the most important crop pollinator
in the United States. However, because of disease and other factors the number
of managed honey bee hives in the United States has declined by 50 percent
since. During this same period, the amount of crop acreage requiring bee
pollination has continued to grow. This makes native pollinators even more
important to the future of agriculture.
Native bees provide free pollination services (as
opposed to honey bee which are typically rented) and are often specialized for
foraging on particular flowers, such as squash, berries or orchard crops. This
specialization results in more efficient pollination and the production of
larger and more abundant fruit from certain crops. The pollination done by
native bees contributes an estimated $3 billion worth of crop production
annually to the U.S. economy.
Native bees come in a wide range of colors and sizes,
from tiny sweat bees less than a quarter of an inch long to bumble bees over an
inch in length. Most are solitary, with each female creating and provisioning
her nest without the support of a caste system of workers.
About 70 percent of native bees excavate underground
nests while 30 percent of bees nest in wood tunnels, usually pre-existing holes
such as those made by wood-boring beetles, but some will chew out the center of
pithy twigs. In the case of both ground-nesting and wood-nesting bees, once the
nest is complete, the mother bee generally dies. Her offspring will remain in
the nest, passing through the egg, larva and pupa stages before emerging as an
adult to renew the cycle. For some species this life cycle may progress over a
matter of weeks, resulting in a second generation of bees in a single season. A
few species may remain dormant for over a year. Most solitary bees however
complete this life cycle over the course of a full year.
Native bees often only live for a few weeks as
actively flying adults. They mate immediately upon emergence and the females
begin nesting. They lay relatively few eggs compared to other insects, with a
single female often laying less than 50 eggs before she dies. Male bees do not
live long beyond mating, they do not collect pollen and have little value as pollinators.
While most of these wood-nesting and ground-nesting
bees are solitary, some are gregarious, preferring to nest near others, a
behavior that allows large aggregations to develop in favorable locations. Only
a few tunnel and ground-nesting bee species ever develop truly social colonies,
and often such behavior is environmentally dependent with some bees being
social in one situation and being solitary in another. The one group of
strictly social bees native to the United States is the group of approximately
45 bumble bee species.
The two habitat components need to be close enough
together so that the bees can fly between them. The flight distance of a bee
varies with the size of the bee. Small sweat bees and mining bees may not fly
more than 200 or 300 yards from nest to forage area. Large bees (bumble bees,
for example) can cross a mile or more of inhospitable, flower-less landscape to
forage. But however large the bee, if it has to fly too far the effort begins
to outweigh the benefits and the bee may either find somewhere else to nest or
not survive in the landscape.
A third factor that influences habitat is insecticide
exposure. To thrive, bees need minimal exposure to pesticides.
Apidae
The
Apidae are a large family of bees, comprising the
common honey bees, stingless bees (which are also cultured
for honey), carpenter bees,
orchid bees, cuckoo bees, bumblebees, and various other less
well-known groups. The family Apidae presently includes all the genera that
were previously classified in the families Anthophoridae and Ctenoplectridae, and most of these are
solitary species, though a few are also cleptoparasites. The four groups that were
subfamilies in the old family Apidae are presently ranked as tribes within the
subfamily Apinae. This trend has been taken to its
extreme in a few recent classifications that place all the existing bee
families together under the name "Apidae" (or, alternatively, the
non-Linnaean clade "Anthophila"),
but this is not a widely-accepted practice.
Stingless Bees.
These can be found in most tropical or subtropical regions of the world,
such as Australia, Africa, Southeast
Asia, Central America and parts of Mexico and Brazil. The
majority of native social bees of Central and South America are stingless bees, although only a
few of them produce honey on a scale such that they are farmed by humans. They
are also quite diverse in Africa and are farmed there also; meliponine
honey is prized as a medicine in many African communities.
Being tropical,
stingless bees are active all year round, although they are less active in
cooler weather. Unlike other eusocial bees, they do not sting but will defend
by biting if their nest is disturbed. In addition, a few have mandibular
secretions that cause painful blisters. Despite their lack of a sting,
stingless bees, being social, may have very large colonies made formidable by
way of numerous defenders.
Stingless bees usually nest in hollow trunks, tree
branches, underground cavities, or rock crevices but they have also been
encountered in wall cavities, old rubbish bins, water meters, and storage
drums. Many beekeepers keep the bees in their original log hive or transfer them to a wooden box, as
this makes it easier to control the hive.
The bees store pollen and honey in large egg-shaped
pots made of beeswax,
typically mixed with various types of plant resin (sometimes called "propolis").
These pots are often arranged around a central set of horizontal brood combs,
where the larval bees are raised. When the young worker
bees emerge from their cells, they tend to remain inside the hive (much like
honey bees, performing different jobs. As workers age, they become guards or
foragers. Unlike the larvae of honey bees,
stingless bee larvae are not fed directly by worker adults. The pollen and
nectar are placed in a cell, an egg is laid, and the cell is sealed until the
adult bee emerges after pupation ("mass provisioning"). At any one
time, hives can contain anywhere from 300-80,000 workers, depending on species.
In a simplified sense, the sex of each bee depends on the number of chromosomes it receives. Female bees have two sets
of chromosomes (diploid)
- one set from the queen and another from one of the male bees
or drones.
Drones have only one set of chromosomes (haploid),
and are the result of unfertilized eggs, though inbreeding can result in
diploid drones.
Unlike true honey bees,
whose female bees may become workers or queens strictly depending on what kind
of food they receive as larvae (queens are fed royal jelly and workers are fed pollen), the caste
system in meliponines is variable, and commonly based simply on the amount of
pollen consumed; larger amounts of pollen yield queens in the genus Melipona.
There is also a genetic component however, and as much as 25% (typically 5-14%) of the female brood may be
queens. Queen cells in the former case can be distinguished from others by
their larger size, as they are stocked with more pollen, but in the latter case
the cells are identical to worker cells, and scattered among the worker brood.
When the new queens emerge, they typically leave to mate, and most die. New nests are not established via
swarms, but by a procession of workers who gradually construct a new nest at a
secondary location. The nest is then joined by a newly-mated queen, at which
point many workers take up permanent residence and help the new queen raise her
own workers. If a ruling queen is herself weak or dying, then a new queen can
replace her. For Plebeia quadripunctata, although less
than 1% of female worker cells produce dwarf queens, they comprise six out of
seven queen bees, and one out of five proceed to head colonies of their own.
They are reproductively active but less fecund than large queens.
Myan Stingless Bees-Melipona beecheii and Meliopons. yucatanica,
These are the only native bees cultured to any degree in the Americas. They were
extensively cultured by the Maya for honey, and regarded as sacred.
These bees are endangered due to massive deforestation, altered agricultural practices (especially insecticides),
and changing beekeeping practices with the arrival of the Africanized honey bee, which produces much
greater honey crops.
These bees have been
kept by the lowland Maya for thousands of years. The
traditional Mayan name for this bee is Xunan kab, literally meaning "royal
lady". The bees were once the subject of religious ceremonies and were a
symbol of the bee-god Ah-Muzen-Cab,
who is known from the Madrid Codex.
The bees were, and still are, treated as pets.
Families would have one or many log-hives hanging in and around their house.
Although they are stingless, the bees do bite and can leave welts similar to a
mosquito bite. The traditional way to gather bees, still favored amongst the
locals, is to find a wild hive; then the branch is cut around the hive to
create a portable log, enclosing the colony (Figure 37). This log is then
capped on both ends with another piece of wood or pottery and sealed with mud.
This clever method keeps the melipine bees from mixing their brood, pollen, and
honey in the same comb as the European bees. The brood is kept in the middle of
the hive, and the honey is stored in vertical "pots" on the outer
edges of the hive. A temporary, replaceable cap at the end of the log allows
for easy access to the honey while doing minimal damage to the hive. However,
inexperienced handlers can still do irreversible damage to a hive, causing the
hive to swarm and abscond from the log. On the other hand, with proper
maintenance, hives have been recorded as lasting over 80 years, being passed
down through generations. In the archaeological record of Mesoamerica, stone
discs have been found which are generally considered to be the caps of long-disintegrated
logs which once housed the beehives.
Traditional Stingless Bee Hive.
Image Courtesy of en.wikipedia.org/wiki/Image:Belize37.jpg
Balché, an alcohol beverage similar to mead, was made from
fermented honey and the bark of the leguminous Balché tree (Lonchocarpus violaceus),
hence its name. It was traditionally brewed in a canoe. The drink was known to
have entheogenic properties, that is, to produce
mystical experiences, and was consumed in medicinal and ritual practices. The hallucinogenic properties come from tan alkaloid in
the bark of the Balché tree, although whether the hallucinogens came from the
bark or the honey, which beekeepers would harvest after placing the nests near
the trees, remains uncertain. Toxic and hallucinogenic substances can be found
in all honey, if bees collect nectar and pollen from certain types of
vegetation. Most likely, it is a combination of the two, since balché is made
from both the Melipona honey gathered from the Balché
flowers, and from the bark of the tree, brewed and fermented together.
Lost-wax casting, a common metalworking method
which is typically found where the inhabitants keep bees, was also utilized by
the Maya. The wax from Melipona is soft and easy to work, especially
in the humid Mayan lowland. This allowed the Maya to create smaller works of
art and jewelry that would be difficult to forge. It also makes use of the
leftovers from honey extraction. If the hive was damaged beyond repair, the
whole of the comb could be used, thus using the entire hive. With experienced
keepers, though, only the honey pot could be removed, the honey extracted, and
the wax used for casting or other purposes.
The outlook for meliponines in Mesoamerica is grim.
The number of active Melipona beekeepers is rapidly declining in
favor of the more economical, non-indigenous Africanized Apis
mellifera. The high honey yield, 100 kilograms or more annually,
along with the ease of hive care and ability to create new hives from existing
stock, commonly outweighs the negative consequences of "killer bee"
hive maintenance. Furthermore, there are flora that the Africanized honey bees do not visit, such as those in the tomato family,
and several forest trees and shrubs, which rely on the native stingless bees
for pollination. There has already been a decline in populations of native
flora in areas where stingless bees have been displaced by Africanized honey
bees. An additional blow to the art of meliponine beekeeping is that many of
the meliponine beekeepers are now elderly men and women, whose hives may not be
cared for once they die. The hives are considered similar to an old family
collection, to be parted out once the collector dies or to be buried in whole
or part along with the beekeeper upon death. In fact, a survey of a
once-popular area of the Mayan lowlands shows the rapid decline of beekeepers,
down to around 70 in 2004 from thousands in the late 1980s. It is traditional
in the Mayan lowlands that the hive itself or parts of the hive be buried along
with the beekeeper to volar al
cielo, "to fly to heaven". There are conservation efforts
underway in several parts of Mesoamerica.
South American Stingless Bee-Trigona spinipes. This is a species
of stingless bee
occurring in South America where it is called arapuá, irapuá or abelha-cachorro ("dog-bee")
(Figure 38.). The species name means "spiny feet" in Latin. Trigona spinipes builds its nest on trees (or on
buildings and other human structures), out of mud, resin, wax, and assorted
debris, including dung. Therefore, its honey is not especially fit for
consumption, even though it is reputed to be of good quality by itself, and is
used in folk medicine. Colonies may have from 5000 to over 100 000 workers.
Adult and Nest of South American Stingless Bees. Images Courtesy of Reynaldo and (Left) Jorge Stolfi
This species will attack in swarms when they feel the
nest is threatened. They cannot sting, and their bite is not very effective but
quite annoying. Their main weapon against predatory animals (including people)
is to get themselves entangled in the victim's hair and buzz loudly. These bees
uses odor trails, sometimes extending to several hundred yards in order lead nest mates from the
hive to a food source. Moreover they will frequently follow trail similar
chemicals used by other bee (such as carpenter
bees, Africanized honeybees and other stingless bees) for the same
purpose, frequently killing or driving them away and taking over their food
source.
This bee has been considered an agricultural pest for
some cultures, such as passion fruit,
because it damages leaves and flowers while collecting nest materials, and
tunnels through the unopened flowers to collect the nectar (thus frustrating
their normal pollinators).[ On the other hand, they are significant
pollinators on their own, e.g. for onions.
Attack by stingless bee although not considered
dangerous to humans can be very annoying if not scary, especially if the victim
is not expecting it. On one occasion Pat
(my wife) and I were collecting insects in Monte Verde Costa Rica. Without any warning there were hundreds of
bees on us. As indicated above they got into our clothing and hair. As indicated their bite was not especially
painful but when hundreds of bees are biting you especially around the face
neck and other areas of the face it can be disconcerting to say the least. She
still talks about it today (30 years ago).
Carpenter Bees. Carpenter bees are large, hairy bees with over 500
species distributed worldwide. Their
name comes from the fact that nearly all species build their nests in burrows
in dead wood, bamboo, or structural timbers.
In the United States,
there are two eastern species, Xylocopa virginica, and Xylocopa micans, and
three other species that are primarily western in distribution, Xylocopa varipuncta, Xylocopa
tabaniformis orpifex and Xylocopa californica. X. virginica is by far the more widely distributed
species. Some are
often mistaken for a bumblebee species,
as they can be similar in size and coloration, though most carpenter bees have
a shiny abdomen, while in bumblebees the abdomen is completely clothed with
dense hair. Males of some species have a white or yellow face, where the
females do not; males also often have much larger eyes than the females, which
relates to their mating behavior. Male bees are often seen hovering near nests,
and will approach nearby animals. However, males are harmless since they do not
have a stinger.[3] Female carpenter bees are capable of
stinging, but they are docile and rarely sting unless caught in the hand or
otherwise directly provoked.
Many Old World carpenter bees have a special
pouch-like structure on the inside of their thorax called the acarinarium
where certain species of mites (Dinogamasus spp.) reside. The exact nature of the
relationship is not fully understood, though in other bees that carry mites
where the mites are beneficial, feeding either on fungi in the nest, or on other, harmful
mites.
Carpenter bees are traditionally considered solitary
bees, though some species have simple social nests in which mothers and
daughters may cohabit. However, even solitary species tend to be
gregarious. There are two very different mating
systems that appear to be common in carpenter bees, and often
this can be determined simply by examining specimens of the males of any given
species. Species in which the males have large eyes are characterized by a
mating system where the males either search for females by patrolling, or by
hovering and waiting for passing females, whom they then pursue. In the other
type of mating system, the males often have very small heads, but there is a
large, hypertrophied glandular reservoir
in the mesosoma, which releases pheromones into the
airstream behind the male while it flies or hovers. The pheromone advertises
the presence of the male to females.[
These bees come in a variety of sizes although
most are slightly larger than a honey bee.
One of the most common species is the valley carpenter bee that is
characterized by solid black females and golden males. They are as large as or
larger than bumblebees.
Female and Male Valley Carpenter Bees.
As previous indicated these bees nest in wood. Their colonies consist of a series of
tunnel-shaped burrows. As do other bees,
carpenter bees collect pollen to feed to their young. Once collected, the pollen is formed into a
ball about the size of a small marble. A single egg is then deposited on each
ball, which subsequently is compartmentalized within the burrows (Figure
40). Their life cycle is completed in a
few months as the larvae develop on the pollen balls.
A
Tunnel of a Carpenter Bee with Developing Larva and Pupa. Image Courtesy Univar Corporation.
Carpenter bees
are not true social insects as there is no division of labor, but many bees may
occupy the same nesting burrow. The
burrows typically are used year after year and can become rather
extensive. Even though these are wood
infesting insects, rarely do they do any significant damage to homes.
Occasionally
they can be bothersome to the homeowner because the males are especially
aggressive and will fly up to and buzz in a person’s face; however, they are
totally harmless, as male Hymenoptera do not have stingers. The sting of the female is quite painful, but
she is much less aggressive.
In the
telephone industry these bees are referred to as pole bees because they
frequently nests in telephone poles.
Even though they typically do not sting, they buzz linemen and in some
cases this has resulted in injuries as a result of the workers’ attempts to
avoid their harassment. I am aware of
more than one case where linemen have fallen from poles due to “bee attack”.
Bumble Bees. A bumblebee (or bumble bee) is any member of the bee genus Bombus, in the family Apidae.
There are over 250 known species, existing primarily in the Northern Hemisphere although they are common in New Zealand and Tasmania.
Bumblebees are social insects that are characterized by
black and yellow body hairs, often in bands. However, some species have orange
or red on their bodies, or may be entirely black (Figure 41). Another obvious (but not unique)
characteristic is the soft nature of the hair (long, branched setae), called pile, that
covers their entire body, making them appear and feel fuzzy. They are best
distinguished from similarly large, fuzzy bees by the form of the female hind
leg, which is modified to form a shiny
concave surface that is bare, but surrounded by a fringe of hairs used to
transport pollen (in similar bees, the hind leg is
completely hairy, and pollen grains are wedged into the hairs for transport).
Like their relatives the honey bees,
bumblebees feed on nectar and gather pollen to feed their young.
One characteristic of bees in general is that the body hairs are profusely
branched making them more efficient in trapping pollen. Their mouthparts consist of a tube-like proboscis
for siphoning the nectar from pants. It
is coiled up when not in use.
A Bumbles Bee with Uncoiled Proboscis in Preparation for
Removal of Nectar. Image Courtesy FFubs.
Right. Bumblebee with Pollen Trapped on Hairs.
Image Courtesy of Jesse Hickman
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The brightly-colored pile of the bumble bee is a form of aposematic signal, meaning the bright coloration
is a sign that I am bad-don’t mess with me
(Figure 42). Depending on the species these colors can range from
entirely black, to bright yellow, red, orange, white, and pink. Thick pile can
also act as insulation to keep the bee warm in cold weather. Further, when
flying a bee builds up an electrostatic charge, and as flowers are usually well
grounded, pollen is attracted to the bee's pile when it lands. When a pollen
covered bee enters a flower, the charged pollen is preferentially attracted to
the stigma (female part of plant-thus fertilization
occurs) because it is better grounded than the other parts of the
flower.
Brightly Colored Bumble Bee. Image Courtesy Christian Sand.
Bumblebees are typically found in higher latitudes and or high altitudes;
though exceptions exist (there are a few lowland tropical species). A few species range into very cold
climates where other bees might not be found; Bombus.
polaris can be found in
northern Ellesmere
Island (west of Greenland)—the northern most occurrence of any true social insect. One reason for this is that bumblebees
can regulate their body
temperature, via solar
radiation, internal mechanisms of "shivering" and cooling
from the abdomen (called heterothermy).
Bumblebee colonies are usually much less extensive
than those of honey bees. This is due to a number of factors including: the
small physical size of the nest cavity, a single female is responsible for the
initial construction and reproduction that happens within the nest, and the
restriction of the colony to a single season (in most species). Often, mature
bumblebee nests will hold fewer than 50 individuals and are typically found
below ground (Figure 43). They sometimes
construct a wax canopy over the top of their nest for protection from moisture
and insulation. Bumblebees do not often preserve their nests through the
winter, though some tropical species live in their nests for several years (and
their colonies can grow quite large, depending on the size of the nest cavity).
In temperate species, the last generation of summer includes a number of queens who overwinter separately in protected spots.
Bumblebees Nest in a Shed. Image Courtesy Pete Griggs.
Bumblebee nests are first constructed by over-wintered
queens in the spring. Upon emerging from hibernation,
the queen collects pollen and nectar from flowers and searches for a suitable
nest site. The characteristics of the nest site vary among species, with some
preferring to nest in underground holes and others in tussock grass or directly
on the ground. Once the queen has found a site, she prepares wax pots to store
food and wax cells into which eggs are laid. These eggs then hatch into larvae, which cause the
wax cells to expand into a clump of brood cells.
These larvae need to be fed both nectar for carbohydrates and protein in order to develop. Bumblebees feed
nectar to the larvae by chewing a small hole in the brood cell into which
nectar is regurgitated. Larvae are fed pollen in one of two ways, depending on
the species. So called "pocket-maker" bumblebees create pockets of
pollen at the base of the brood cell clump from which the larvae can feed themselves.
Conversely, "pollen-storers" store pollen in separate wax pots and
feed it to the larvae in the same fashion as nectar. Bumble bees are incapable of trophallaxis (direct transfer of food from one bee
to another) which is common in other hymenoptera such as ants.
After the emergence of the first or second group of
workers, workers take over the task of foraging and the queen spends most of
her time laying eggs and caring for larvae. The colony grows progressively
larger and at some point will begin to produce males and new queens. The point
at which this occurs varies among species and is heavily dependent on resource
availability and environmental factors. Unlike the workers of more advanced social
insects, bumblebee workers are not physically reproductively sterile
and are able to lay haploid eggs that develop into viable male
bumble bees. Only fertilized queens can lay diploid eggs that mature into workers and new
queens.
Early in the colony cycle, the queen bumblebee
compensates for potential reproductive competition from workers by suppressing
their egg-laying by way of physical aggression and pheromonal signals. Thus,
the queen will usually be the mother of all of the first males laid. Workers
eventually begin to lay males later in the season when the queen's ability to
suppress their reproduction diminishes. The reproductive competition between workers and the queen is one
reason that bumble bees are considered "primitively social
insects".
New queens and males leave the colony after
maturation. Males in particular are forcibly driven out by the workers. Away
from the colony, the new queens and males live off nectar and pollen and spend
the night on flowers or in holes. The queens are eventually mated (often more
than once) and search for a suitable location for diapause
(dormancy). The following season they will form new colonies.
Bumblebees generally visit flowers exhibiting the bee pollination syndrome. They can visit
patches of flowers up to 1-2 kilometers from their colony. Bumblebees will also tend to visit the
same patches of flowers every day, as long as nectar and pollen continue to be
available. While foraging,
bumblebees can reach ground speeds of up to 15 m/s (54 km/h).
When bumblebees arrive at a flower, they extract
nectar using their long tongue. Many
species of bumblebee also exhibit what is known as "nectar robbing":
instead of inserting the mouthparts into the flower normally, these bees bite
directly through the base of the flower
to extract nectar, avoiding pollen transfer. These
bees obtain pollen from other species of flowers that they “legitimately”
visit.
Pollen is removed from flowers deliberately or
incidentally by bumblebees. Incidental removal occurs when bumblebees come in
contact with the anthers of a flower while collecting nectar.
The bumblebee's body hairs receive a dusting of pollen from the anthers which
is then groomed into the pollen
baskets.
Bumblebees are also capable of pollination. With certain species of
plants it I difficult to remove the pollen from the anthers. In order to release the pollen, bumblebees and some
species of solitary bees are able to grab onto the flower and move their flight
muscles rapidly, causing the flower and anthers to vibrate, dislodging pollen.
This resonant
vibration is called buzz pollination. The honeybee rarely
performs buzz pollination. About 8% of the flowers of the world are primarily
pollinated using buzz pollination. This behavior is very important for
some plants such as blueberries, cranberries, tomatoes and peppers, all of
which release pollen from pores within the anthers (similar to salt being
shaken from a salt shaker).
In at least a few species, once a bumblebee has
visited a flower, it leaves a scent mark on the flower. This scent mark deters
visitation of the flower by other bumblebees until the scent degrades wears
off. It has been shown that this
scent mark is a general chemical bouquet that bumblebees leave behind in
different locations (e.g. nest, neutral, and food sites) and they learn to use this bouquet to
identify both rewarding and unrewarding flowers. In addition, bumblebees rely on this
chemical bouquet more when the flower has a high handling time (i.e. it takes a
longer time for the bee to find the nectar).
Once they have collected nectar and pollen, bumblebees
return to the nest and deposit the harvested nectar and pollen into brood
cells, or into wax cells for storage. Unlike honey bees,
bumblebees only store a few days' worth of food and so are much more vulnerable
to food shortages.
Providing Nest Locations for Bumble Bees. Unlike
solitary bees, which can be very particular about tunnel diameters, bumble bees
are flexible in their nesting needs. All they want is a warm, dry cavity,
roughly the size of a shoebox (Figure 44). Artificial nests can be constructed
to attract bumble bees, but occupancy is typically extremely low – often far less
than 25 percent.
A simple wooden bumble bee box can be made from
preservative-free lumber. An appropriate size will have internal dimensions of
about 7 inches high by 7 inches wide and 7 inches long. Drill a few ventilation
holes on the upper sides of the box (near the roof) and cover with window
screen to deter ants. Also drill some drainage holes in the bottom. Make an
entrance tunnel from 3/4-inch diameter plastic pipe and fill the box with soft
bedding material, such as short lengths of soft unraveled string, dry straw or
upholsterer's cotton (do not use cotton balls, as the fibers become tangled in
the bees' legs). The box must be weather tight; if the nest gets damp, the
larvae may become too cold and mold and fungus will grow.
Bumble Bee Box.
Place the nest in a dry, undisturbed area that has
some obvious landmarks (a fence post, rock or building) to aid bee navigation;
these landmarks are important to bees returning from foraging. Nesting boxes
that are at ground level or slightly buried (either with soil or straw) are the
most attractive to queens of many species. Boxes placed on the surface should
be level and stable. If you are burying your box, extend the entrance pipe so
it gently slopes up to the surface and clear the vegetation from an area a few inches
around where the pipe surfaces.
The best time to install a bumble bee nest box is in
early spring, when the first queens have emerged from hibernation and are
searching for a nest site; in many areas, this is when the willows first start
blooming.
Bumble bee nests require little maintenance. Watch
your boxes through the spring and early summer. Any above-ground boxes that are
unoccupied by late July can be removed, cleaned and put into storage until the
following spring. This is not vital, and if you have a lot of boxes on a large
site it may not be practical. In late fall or early winter inspect all the
boxes that have been occupied. Remove the old nests, clean them and make any
repairs. Cleaning the boxes with a bleach-water solution (1:2 ratios) will help
reduce parasites and diseases in the nests. The following spring, add fresh
nesting material to all the boxes.
The package bumble bee industry, which provides
farmers with live bumble bee colonies for crop pollination, currently only
produces a single eastern bumble bee species, Bombs impatiens. This
species is then shipped nationwide, in a situation similar to the blue orchard
bee, often far beyond its native range. Many bumble bee scientists now believe
that these commercially produced bumble bees are responsible for the
introduction of one or more diseases which have decimated several bumble bee
species, even causing the potential extinction of one species, Bombus franklini (Franklin's bumble bee).
There is an enormous need for managed agricultural
pollinators in this country, but it critical not to import non-local bees,
especially near wild areas, even if the bees are represented as being the same
species as local bees. The alternatives are to either develop local commercial
sources of bees that are native to your region or to rear already widely
established non-native species, such as honey bees or the alfalfa leafcutter
bee, as managed pollinators.
Cuckoo bumblebees are a few species of bees which live parasitically in the colonies of other bumblebees
and have lost the ability to collect pollen (Figure 45).. Before finding and
invading a host colony, a Psithyrus female (there is no caste system in
these species) will feed directly from flowers. Once she has infiltrated a host
colony, the Psithyrus female will kill or subdue the queen
of that colony and forcibly (using pheromones and/or physical attacks)
"enslave" the workers of that colony to feed her and her young. This
female also has a number of
adaptations, such as larger mandibles and a larger venom sac that increase her
chances of taking over a nest.
Cuckoo Bumblebee. Image Courtesy of Alvesgaspar.
Queen and worker bumblebees can sting,
but unlike a honey bees,
a bumblebee's stinger lacks barbs, so they can sting more than once. Bumblebee species are normally
non-aggressive, but will sting in defense of their nest, or if harmed. Female
cuckoo bumblebees will aggressively attack host colony members, and sting the
host queen, but will ignore other animals (including humans) unless
disturbed. Based on my numerous
encounters the sting of the bumble bees is considerably more painful than that
of a honey bee.
Bumblebees are important pollinators of both crops and wildflowers.
Bumblebees are increasingly cultured for agricultural use as pollinators
because they can pollinate plant species that other pollinators cannot by using
a technique known as buzz pollination. For example, bumblebee colonies are
often emplaced in greenhouse tomato production, because the frequency of
buzzing that a bumblebee exhibits effectively releases tomato pollen which is
normally wind pollinated and therefore difficult to release from the anther.
Bumblebees are in danger in many developed countries
due to habitat destruction and collateral pesticide damage. In Britain,
until relatively recently, 19 species of native true bumblebee were recognized
along with six species of cuckoo bumblebees. Of these, three have become extinct, eight are in serious decline, and only six remain
widespread. Similar declines in bumblebees have been reported in Ireland, with
4 species being designated Endangered, another two species considered Vulnerable to
extinction. A decline in
bumblebee numbers could cause large-scale sweeping changes to the countryside,
leading to inadequate pollination of certain plants. The world's first
bumblebee sanctuary was established at Vane Farm in the Loch Leven National
Nature Reserve in Scotland in 2008.
One common, yet incorrect, assumption is that the buzzing sound of bees is caused by the beating
of their wings. The sound is actually the result of the bee vibrating its
flight muscles, and
this can be achieved while the muscles are decoupled from the wings—a feature
known in bees but not other insects. This is especially pronounced in
bumblebees, as they must warm up their bodies considerably to get airborne at
low ambient temperatures. Bumblebees
have been known to reach an internal thoracic temperature of 30 °C
(86 °F) using this method.
The orchestral interlude "Flight of the Bumblebee" was composed
by Rimsky
Korsakov to represent
the turning of Prince Guidon to visit his father, Tsar Saltan, in the opera The Tale of Tsar Saltan, however the music is considered to
more accurately reflect the flight of a bluebottle
fly rather than a
bumblebee.
The music went on to inspire Walt Disney to have a bumblebee featured in his
musical Fantasia and also sound as if it was flying in
all parts of the theatre - the unsuccessful experimentation led to the music
being excluded from the film and the eventual invention of surround
sound.
Salvador Dali was
inspired by the sound of a bumblebee to create one of his paintings Dream Caused by the Flight of a
Bumble bee around a Pomegranate a Second before Awakening.
Orchid
Bees. Euglossine bees, also
called orchid bees, are the only group of corbiculate bees whose non-parasitic members do
not all possess eusocial
behavior. Most of the species are solitary, though a few are
communal, or exhibit simple forms of eusociality. There are about 200 described species,
distributed in five genera: Euglossa, Eulaema, Eufriesea, Exaerete and the monotypic Aglae,
all exclusively occurring in South or Central America (though one species, Euglossa viridissima,
has become established in the United States).
The latter two genera are cleptoparasites in the nests of other orchid bees. All
except Eulaema are characterized by brilliant
metallic coloration, primarily green, gold, and blue (Figure 46).
A
Nest of Orchid Bees.
Females gather pollen and nectar as food from a
variety of plants, and resins, mud and other materials for nest building. Some
of the same food plants are also used by the males, which however leave the
nest upon hatching and do not return.
Male orchid bees have uniquely modified legs which are
used to collect and store different volatile compounds (often esters) throughout their
lives, primarily from orchids in the subtribes Stanhopeinae and Catasetinae,
where all species are exclusively pollinated by euglossine males. These orchids
do not produce nectar, and hide the pollen on a single anther under an anther cap; they are not
visited by females. The whole pollinarium becomes attached to the male as it
leaves the flower (Figure 47). Several flowers from other plant families are
also visited by the bees: Spathiphyllum and Anthurium (Araceae), Drymonia and Gloxinia (Gesneriaceae),Cyphomandra (Solanaceae),
and Dalechampia (Euphorbiaceae)
contain one or more species that attract male euglossines.
A
Male Orchid Bee with Highly Modified Legs. Image Courtesy Green Fly.
The chemicals are picked up using special brushes on
the forelegs, transferred from there by rubbing the brushes against combs on
the middle legs, and finally these combs are pressed into grooves on the dorsal
edge of the hind legs, squeezing the chemicals past the waxy hairs which block
the opening of the groove, and into a sponge-like cavity inside the hind tibia.
The accumulated "fragrances" are evidently
released by the males at their display sites in the forest understory, where
matings are known to take place. Although
the accumulated volatiles have long been believed to serve as a signal to
females, female attraction to male odors has never been demonstrated in
behavioral experiments. The behavior of volatile collection is essentially
unique in the animal kingdom. Single synthetic compounds are commonly used as
bait to attract and collect males for study, and include many familiar flavorings
and odors considered appealing to humans (e.g., methyl
salicylate, eugenol, cineole, benzyl
acetate, methyl benzoate, methyl
cinnamate), and others which are not (e.g., skatole).
Neotropical orchids themselves often exhibit elaborate
adaptations involving highly specific placement of pollen packets (pollinia)
on the bodies of the male orchid bees; the specificity of their placement
ensures that cross-pollination only occurs between orchids of the
same species. Different orchid bee males are attracted to different chemicals,
so there is also some specificity regarding which orchid bees visit which types
of orchid. The early description of this pollination system was by Charles
Darwin, though at the time, he believed the bees were females. Not all orchids utilize euglossines as
pollen vectors, of course; among the other types of insects exploited are other
types of bees, wasps, flies, ants, and moths.
The male Eufriesea purpurata is highly unusual in actively
collecting the insecticide DDT in huge amounts from houses in Brazil, without
suffering any harm from it.
Digger Bees. The Anthophorini is a large tribe in the family Apidae, with
over 750 species worldwide that were previously classified in the family Anthophoridae;
the vast majority of species are in the genera Amegilla and Anthophora.
All species are solitary, though many nest in large aggregations. Nearly all
species make nests in the soil, either in banks or in flat ground; the larvae
develop in cells with waterproof linings and do not spin cocoons.
Species in this tribe are often referred to as "digger bees", though this common name is sometimes applied to
members of the tribe Centridini,
as well (Figure 48).
Digger Bee, Image Courtesy of
entomart.
The characters used to define this group are subtle,
but they are nonetheless fairly recognizable; they are generally large (up to
3 cm), very robust, hairy bees, with visibly protruding faces, and the
apical portion of the wings are studded with microscopic papillae.
The abdomen is often banded, and in many Old World species of Amegilla these bands are metallic blue. The
wings often appear disproportionately short compared to other bees, and their
"buzz" is often a high-pitched whine, as they hover and feed on
flowers. Males commonly have pale white or yellow facial markings, and/or
peculiarly modified leg armature and hairs.
Attracting Digger Bees. Some digger bees nest in
cracks or cavities in soft sandstone and dry exposed soil embankments. Some of
these species will excavate tunnels in cliff sides by wetting the hard soil
surface with water or nectar to soften it.
To attract these species, adobe bricks can serve as
the equivalent of a wooden nest block. Such bricks can sometimes be purchased,
in which case you can increase their attractiveness to bees by drilling nesting
holes following the size recommendations listed above for wood blocks.
Adobe blocks can also be easily made where clay soils
are common. To create one, half-fill a large bucket with clay soil, and then
fill the bucket with water. Stir the mixture together to create muddy slurry
and allow it to settle. Remove any sticks or debris floating on the surface and
slowly pour off most of the water. Finally, pour the remaining sediment into a
mold (such as a wooden box or small Styrofoam cooler), and allow it to dry for
several days or weeks. Before it completely dries, you can make several 1-inch indentations,
using the diameter guidelines above, to make it more attractive to bees.
Mount the brick, either singularly or in a stack.
Adobe will not hold up well in wet climates and many need sheltering from rain.
You might want to supply a shallow water source near your bricks to help bees
excavate their nests.
Halictidae-Halictid
Bees. This is a cosmopolitan family of the order Hymenoptera consisting of small (> 4 mm)
to midsize (> 8 mm) bees which are usually dark-colored and
often metallic in appearance. Several species are all or partly green and a few
are red (Figure 49); a number of them
have yellow markings, especially the males, which commonly possess yellow
faces, a pattern widespread among the various families of bees. They are commonly
referred to as sweat bees (especially the smaller species), as
they are often attracted to perspiration;
when pinched, females can give a minor sting.
Common Sweat Bee. Image Courtesy of Jon Sullivan
Most halictids nest in the ground, though a few nest in
wood. They mass-provision their young by providing a mass of pollen and nectar
formed inside a waterproof cell. Once an
egg is deposited on this mass the cell is sealed off. Thus the larva is with all the food at one
time that it needs for full development, as opposed to "progressive
provisioning", where a larva is fed repeatedly as it grows, as in honey bees.
All adult species are pollen feeders and may be important pollinators.
Several genera and species of halictids are cleptoparasites of other bees (mostly other
halictids). The most well-known and common are species in the genus Sphecodes, where the
female enters the cell with the
provision mass, eats the host egg, and lays an egg of her own in its place.
Halictidae are one of the four bee families that
contain some species that are crepuscular.
These bees are active only at dusk or in the early evening or sometimes truly
nocturnal. In these cases they have greatly enlarged ocelli
or simple eyes to enhance their night vision.
Megachilidae-Leaf
Cutting Bees and Mason Bees. The Megachilidae are a cosmopolitan family of solitary bees (Figure 50) whose pollen-carrying
structure (called a scopa)
is restricted to the ventral surface of the abdomen (rather than mostly or
exclusively on the hind legs as in other bee families).
Leaf Cutting Bee with Pollen Trapped on Underside of
Abdomen.
Megachilid
genera are most commonly known as mason bees and leafcutter bees, reflecting the
materials they build their nest cells from (soil or leaves, respectively); a
few collect plant or animal hairs and fibers, and are called carder bees. All species feed on
nectar and pollen, but a few are cleptoparasites (informally called "cuckoo bees"),
feeding on pollen collected by other megachilid bees. These parasitic species
do not possess scopa and are incapable
of collecting their own pollen. The brightly colored scopa leads to a
colloquial name used occasionally in North America - "Jelly-belly bees."
Megachilid bees are among the world's most efficient pollinators because of their energetic
swimming-like motion in the reproductive structures of flowers, which moves pollen, as
needed for pollination.
One of the reasons they are efficient pollinators is their frequency of
visiting to plants. In actuality they are extremely inefficient at gathering pollen
when compared to all other bee families. However, megachilids require on
average nearly ten times as many trips to flowers to gather sufficient
resources to provision a single brood cell. Of course with more, more
pollination is accomplished.
North America has many native megachilid species, but Alfalfa leafcutter bees (Megachile rotundata) are an
imported species used for pollination. The most
significant native species is Osmia
lignaria (the
"Orchard Mason Bee" or "Blue Orchard
Bee"), which is sold commercially for use in orchard crop
pollination, and which can be attracted to nest in wooden blocks with holes
drilled in them (which are also sold commercially for this purpose).
Leafcutter
bees nest in soft, rotted wood; thick-stemmed, pithy plants (e.g., rose); and
in similar materials that the bees can easily cut through and excavate. Nest
tunnels may extend several inches deep and coarse sawdust may be deposited at
the entrance. This sometimes causes confusion with other wood nesting insects
such as carpenter ants. However, leafcutter bees restrict their tunneling to
soft, rotted wood and do not cause damage to homes or other wooden structures.
There
also are concerns about leafcutter bee nesting in rose canes, excavating the
pith of pruned canes. Leafcutter bees sometimes nest in the largest diameter
rose canes but cause little damage because they restrict tunneling to the pith
and rarely girdle cambium. Furthermore, other insects, including various
hunting wasps (Pemphredon species) and small carpenter bees more
commonly tunnel and nest in rose canes.
After
the nest is made, the bees collect fragments of leaves to construct individual
nest cells. The bees cut leaves in a distinctive manner, making a smooth
semicircular cut about 3/4 inch in diameter from the edge of leaves. Although
they cut many types of leaves, leafcutter bees prefer certain types, notably
rose, green ash, lilac and Virginia creeper. This injury often is only a minor
curiosity. However, where leafcutter bees are abundant and concentrate on
cultivated plantings, the removal of leaf tissues can be damaging. Serious
damage most often occurs in isolated rural plantings.
Rose Leaf with
Discs Cut from Edge by Leaf Cutting Bee.
Leafcutter
bees do not eat the cut pieces of leaves that they remove. Instead, they carry
them back to the nest and use them to fashion nest cells within the previously
constructed tunnels. Then they provision each leaf-lined cell with a mixture of
nectar and pollen. The female lays an egg and seals the cell, producing a
finished nest cell that somewhat resembles a cigar butt. A series of closely
packed cells are produced in sequence. A finished nest tunnel may contain a
dozen or more cells forming a tube 4 to 8 inches long. The young bees develop
and remain within the cells, emerging the next season.
There are a great many parasites that act as important
natural enemies of leafcutter bees. As a result, leaf cutting activity may vary
widely from year to year. Parasitic bees and wasps, velvet ants and certain
blister beetles are among the most important enemies of leafcutter bees and
other solitary bees.
Alfalfa
Leafcutter Bee-Megachile rotundata. This is a
European bee that has been introduced to other
regions . As a solitary bee species, it does not build colonies or store honey, but is a very
efficient pollinator of alfalfa, carrots and some other vegetables.
The importation of the species to North America was to assist in the pollination of food crops, and it has now
widespread. The
species is also found in Queensland, Australia, but not recorded in
other states. The vernacular in Australia is Lucerne leafcutter bee.
Female alfalfa leafcutter bees have stingers, but both
sexes will use their mandibles as a defensive mechanism, usually only defending
themselves when squeezed or antagonized. Therefore bee suits, such as those
required with honey bees, are not really necessary when dealing with these
bees. The ratio of males to females is generally one to one.
Alfalfa Leaf Cutting Bee. Image Courtesy of USDA.
This species of leafcutter bee is cultivated to
pollinate alfalfa grown for seed, a function that it does far more efficiently
than honeybees. These leafcutter bees are provided with predrilled "bee
boards" that they use for nest construction. At the end of the season, the
nest cells with developing bees are collected and carefully stored, to be
released the subsequent season when alfalfa blooms.
Figure 53. Alfalfa Leaf Cutting Bee
Pollinating Alfalfa.
Commercially produced bee blocks, consisting of a wood
block drilled with a series of dead-end holes, are now widely available. These
types of bee nests were initially developed in the 1960s by alfalfa seed
producers in the western United States to attract and manage large numbers of
the non-native alfalfa leafcutter bee (Megachile
rotundata). Their sole purpose is
to attract wild populations of these bees.
Bee
Block for Attracting Large Population of Alfalfa Leaf Cutting Bees.
More recently they have been modified to manage the
blue orchard bee (Osmia lignaria), a
bee that is active only in the spring and will not pollinate later-flowering
fruits and vegetables. Consequently, all of the nest tunnels are a uniform size
and depth, which may be either too large or too small for many other species.
Nest blocks with a greater diversity of hole sizes and depths are necessary to
attract a variety of bees that are active throughout the year.
Under the best circumstances these nests can attract
large numbers of cavity-nesting bees and boost their local populations.
However, because these nests concentrate bee populations in unnaturally large
numbers in a small space, they can become infested with parasites and disease
spores after several seasons.
Without regular sanitation or the phasing out of nest
materials, these parasites and diseases threaten long-term pollinator health
wherever they are used. Because contaminated nest blocks left unattended in the
landscape continue to attract wild bees from the surrounding area, they have
the potential to do harm. Only with proper management can these nests maintain
healthy bee populations indefinitely.
Alfalfa flowers provide an example of native bee
efficiency. The stamen (the structure holding the anthers) of alfalfa flowers
is held under tension by two flower petals, and springs forward with force when
released by a visiting bee. This triggering discourages many bees, including
honey bees, which learn to avoid being hit by the stamen by approaching the
flower from behind, where they can gather nectar but not pollen. The alkali bee (Nomia melanderi), a native
ground-nesting megachilid bee, is not discouraged by this unusual flower
structure and is a major pollinator of alfalfa seed in some western states. It
has been used as an effective pollinator of alfalfa when grown for seed in the
western United States. In this case large
areas of barren soil are provided for the nesting of this bee,
Mason Bees. These are a gentle beneficial insects that
has potential as a pollinator of apples, cherries, and other tree fruits. It is
found throughout most of North America, particularly in wooded areas but often
around homes in towns and cities.
Mason Bees.
Image Courtesy of Exzellente
Bilder.
Homeowners sometimes become concerned when they see
the bee entering cavities under shake siding or investigating nail holes or
other cavities in wood during March through early June. These are not
destructive insects, since they do not excavate holes in the wood, though they
will clean out loose debris. No controls are recommended, since no damage is
done. To prevent the bee from nesting, holes may be filled with caulking.
The
females use existing holes in wood for a nest. They choose holes slightly
larger than their body, usually 1/4 to 3/8 inches in diameter. The bees first
place a mud plug at the bottom of the hole, then brings in 15 to 20 loads of
nectar and pollen which they collects from spring flowers, including apples and
other fruits. If you watch the bees closely as they enter the nest, you can see
the pollen on the underside of the abdomen.
When
the female has provided a sufficient supply of food for the larva, she lays an
egg and then seals the cell with a thin mud plug. She then provisions another
cell, and continues in this fashion until the hole is nearly full. Finally the
bee plasters a thick mud plug at the entrance. Some wasps and leaf-cutter bees
also build nests in such holes but their nests can be distinguished from the
orchard mason bee nests by characteristics of the plug. The plug of the mason
bee is always rough while the wasp prepares a smooth plug. Leaf-cutters seal
the holes with chewed-up leaves.
Mason Bee Egg in Pollen Mass.
Image Courtesy of Red58bill
The
female mason bee lives for about a month and can produce one or two eggs each
day. The larva hatches from the egg after a few days and begins to eat its
provisions. When the pollen-nectar mass is completely eaten in about 10 days,
the larva spins a cocoon and pupates within the cell.
Near
the end of the summer the bee transforms to the adult stage but remains in the
cocoon throughout the winter. In the spring, when the weather has warmed up
sufficiently, the males begin to emerge by chewing their way out of the cocoons
and through the mud plugs. The females, which are almost always in the inner
cells of the tunnel, emerge several days later. One or two weeks may be
required for all the bees to emerge during cool weather.
Females
mate soon after emerging and begin nesting in 3 to 4 days. The bees forage on a
number of different flowers. In wooded areas, they seem to prefer ballhead
waterleaf. In urban areas, dandelion and Oregon grape are commonly visited, in
addition to cherries and apples.
The
mason bee is non-aggressive and will sting only if handled roughly or if it
should get trapped under clothing. It is less objectionable than the honey bee
as a pollinator in urban areas and should be encouraged. Efforts are being made
experimentally to develop large populations of these bees to use as a
supplement to honey bees for fruit pollination, much as the alfalfa leaf
cutting bee was developed for alfalfa seed pollination.
Populations
for pollinating around a home or commercial orchard can be developed by
establishing trap nests to collect the bees. Trap nests can be made by drilling
holes 1/4 to 3/8 inches in diameter and 3 to 6 inches deep in pine or fir
4x4's. A "brad-point bit" leaves a nice, smooth hole. (Figure 57)
Alfalfa leaf cutting bee boards with hole diameters of at least 1/4 inch can
also be used. These boards are then
attached to a house or other structure where bees have been seen. Some
protection from rain is desirable. Boards can also be placed on dead trees or posts
in wooded areas near streams where there is a good supply of mud for nest
construction and wild flowers on which to forage.
Predrilled Drilled Block Infested with Mason Bees.
Image Courtesy of Red 58bill.
Boards
should be positioned where they will receive morning sunlight and started in
March before the bees begin nesting and remove them in early to mid-summer when
nesting is completed. If the boards are stored outdoors over winter (under
cover to protect them from rain and snow) the bees will usually emerge in March
and April. They should forage for pollen during the period of cherry and apple
bloom and afterwards, if sufficient other flowers are available to them.
For
large populations for orchard pollination, the nests should be under humid
refrigeration at 35 to 40° F. This will permit control of emergence time and
reduce predation and parasitism by the insect enemies of the bees. Do not place
the nests in storage until September or October to assure complete development
of the adults. The following spring, place the boards in the orchards in
plywood shelters facing east to catch the morning sun. To hasten emergence,
incubate the boards at room temperature for 24 hours before placing the bees in
the orchard. The boards and some new nesting material should be in place a few
days before apples begin to bloom, or earlier if other fruit bloom such as
cherries, is available. Provide 500-1000 filled holes per acre. These should
contain 750-1000 females, assuming an average of 1 1/2 females per hole. Males
also visit flowers, but they do not live long and are not as effective as
pollinators. Competing flowers such as dandelions should be mowed as soon as
the fruit begins to bloom.
Developing
large populations of the bees may be a slow process under orchard conditions;
the short duration of bloom does not allow the bees to accomplish maximum
reproduction. The orchard mason bee also has a tendency to fly away rather than
using or reusing nests in the near vicinity. However, relatively large
populations have been developed in 2 or 3 years in urban situations. Once
established, orchard bees will nest in containers filled with large-diameter
drinking straws or paper tubes folded in half.
Orchard
Mason Bee, Osmia
lignaria. This is a megachilid bee that as do other mason bee makes nests
in reeds and natural holes, creating individual cells for their brood that are
separated by mud dividers. They are unlike carpenter
bees in that they
cannot drill holes in wood. O.
lignaria is a common species
used for early spring fruit bloom in Japan, Canada, and the United States,
though a number of species of other Osmia are also cultured for use in pollination.
Orchard Mason Bee. Image Courtesy
Red58bill.
The bees begin to emerge from their cocoons in the
spring when the daytime temperature reaches 14°C (57°F). The males emerge first. They remain
near the nesting site and wait for the females to begin their emergence, which
can be several days to weeks depending on the number of days of warm weather.
The first thing the females do is mate. A female will typically mate once,
maybe twice. She will be absent from the nesting site for several days while
she feeds and waits for her ovaries to fully mature.
When a female is ready, she seeks out a suitable nest. O. lignaria females like to nest in narrow holes
or tubes, though they have been found to nest inside cedar shakes and even
keyholes. Beekeepers put out pre-made nesting materials to entice the females
to stay close to the orchard. Rain, wind, and free-release (the practice of
putting loose cocoons out rather than letting them emerge in their natal nests)
discourage females from selecting a nesting site near their natal nest. A
female might inspect several potential nests before settling in. Once she has
found the right nest, she flies outside of the hole and does an in-flight
dance. She is orienting on major visual features in order to find her nest when
she returns from foraging.
O. lignaria arrange their nest as a series of
partitions, with one egg per partition. She begins the process by collecting
mud and building the back wall of the first partition. Then she makes trips to
nearby flowers. Unlike honey bees which visit flowers that are miles
away, she prefers flowers that are nearest the nest. She can visit 75 flowers
per trip, and it takes 25 trips to create a complete pollen/nectar provision.
She works tirelessly during the day, only stopping once the sun has gone down.
When the sun rises the next morning, she will bask in its rays until she is
warm enough to fly. Then she continues where ever she left off the day before.
Once the provision is complete, she backs into the
hole and lays an egg on top of it. She collects more mud to seal off the
partition. The new wall also doubles as the back wall of the next cell. She
continues until she has filled the nest hole. O.
lignara, like many insects, can select the gender of the egg they lay by fertilizing
the egg, or not. Unfertilized eggs are males, while fertilized eggs are
females. The adult bee lays female eggs in the back of the burrow, and the male
eggs towards the front. She lays about three males to every nest hole depending
on depth.
When the egg hatches, the larva consumes the food
provision as it goes through many changes on its way to becoming an adult. It
will spend most of its life alone in this dark cell made by its mother.
Once the female has finished the nest, she plugs the
entrance with one thick mud wall. Then she seeks out another location for a new
nest. She works tirelessly until she dies. An O.
lignaria female lives for about four to eight weeks and she can complete an
average of four 6-inch tubes in her lifetime, with about eight eggs per tube.
That's nearly 60,000 blossom visits per female. Because of this farmers have
cultivated the insect for pollination purposes in fruit orchards.
By the early summer, a larva has consumed all of its
provisions and begins spinning a cocoon around itself and enters the pupal stage; the adult females die off as
the season progresses.
The young bee is now a fully developed insect and diapauses inside its cocoon for the duration of
the winter. They burn through their fat reserves to stay warm. If it stays cold
for too long, the bees can die of starvation. Alternatively, if the temperature
rises too fast, they may emerge before the blossom. Farmers are known to
exploit their emergence cycle and time their release to coincide with the first
orchard blossoms.
Commercial Availability. Recently, many people have
become interested in the blue orchard bee (Osmia
lignaria), also called the orchard mason bee, as a garden and orchard
pollinator. Many thousands of mason bee nesting blocks are sold each year in
the United States, along with hundreds of thousands of blue orchard bees. This
interest has greatly raised public awareness about the importance of
pollinators; however, it is important to remember that raising large numbers of
a single species (bee-ranching) is a different objective than the conservation
of diverse species of wild pollinators.
As mason beekeeping has increased in popularity,
important questions are being asked about the risks associated with the
nationwide shipment of blue orchard bees by commercial producers. In fact, there
are two distinct subspecies of the blue orchard bee: Osmia lignaria propinqua in western North America and Osmia lignaria lignaria in the east. The species is rare in
the Great Plains region, although some intermediate specimens have been
collected.
Most commercial producers of the blue orchard bee are
located in the Pacific Northwest, where they rear the locally native western
subspecies . Unfortunately, the bees these producers raise are then marketed
nationwide, resulting in the frequent shipment of locally non-native bees to
the eastern United States. The potential ecological consequences of the western
blue orchard bee hybridizing with its eastern subspecies are unknown.
Similarly, these shipments have the potential to introduce locally non-native parasites
and diseases. For the consumer, there is another significant drawback. The
western bees may not develop in sync with local conditions, resulting in poor
establishment and poor performance as pollinators. The net result is that
people purchasing blue orchard bees over the Internet or through garden
catalogs may be doing more to harm their local pollinator populations than to
help them – and not be getting the pollination they paid for.
Colletidae-Colletid
Bees
This is a family of bees that are often
referred to collectively as plasterer bees, due to the method of
smoothing the walls of their nest cells with secretions applied with their
mouthparts; these secretions dry into a cellophane-like lining. This allows the
bees to nest in periodically flooded areas such as stream banks. There are over
2000species,
all of them evidently solitary, though many nest in aggregations. Bees in this
are highly varied in appearance and have few common features. One feature
consistent to all colletid bees is that their tongue has a branched tip (Figure
59) . The two genera most frequently seen are Colletes and Hylaeus.
Two of the subfamilies, Euryglossinae and Hylaeinae, lack the
external pollen-carrying apparatus (the scopa)
that otherwise characterizes most bees, and instead carry the pollen in their
crop (enlarged portion of the foregut). These groups, and in fact most genera
in this family have liquid or semi-liquid pollen masses on which the larvae
develop.
Colletid Bee. Image Courtesy of Michael Becker.
They can be found all over the world, but the most
species live in South America and Australia.
Over 50% of all bee species living in Australia belong to this family. Only the
genera Colletes and Hylaeuscan
be found in Europe, while
in North America there are, in addition to these two,
the genera Caupolicana, Eulonchopria, and Ptiloglossa.
ANTS
Ants are among the most highly evolved of insects. The
variety of lifestyles displayed by ants is amazing--perhaps because so many of
their social behaviors seemingly parallel our own.
All living ant species have a caste system. The main
castes consist of kings, queens and workers. The kings are winged reproductive
males that contribute absolutely nothing to the labor of the colony. The winged
females swarm with the males, similarly to the behavior previously discussed
with termites. Eventually they will become the queens of new colonies. During
the establishment of a new colony, the new queen initially performs all the
work tasks; but once her first brood of worker larvae is reared to adulthood,
her sole duty is to lay eggs. Unlike termites, ant colonies may have many
queens, in some cases, hundreds.
Workers are sterile females and can be both the
laborers and defenders of the colony. In most ant species there can be
sub-castes of the workers, namely majors, media and minors. Relative head and
overall body size distinguish subcastes. The majors are the largest of the
three and possess a disproportionately large head and mandibles. The function
of the soldiers is to protect the ant colonies. The media and minor workers are
the most common individuals in an ant colony and perform the majority of the
work duties. Minor worker ants also perform a variety of functions depending on
the species of ant.
Ant Wars, Competition and Survival. Ants are amongst the most aggressive and
war-like of all animals. If ants had a
policy of life it could be summarized as restless aggression, territorial
conquest, and total annihilation of neighboring colonies. These insects use any of a number of strategies
and weapons to reach these ultimate goals.
Chemical warfare is prevalent amongst many species including spraying a
variety of toxic chemicals in order to repel, confuse, immobilize or even kill
their rivals. The soldiers of many
species readily assume a kamikaze role in order to “win skirmishes” between
rival colonies. One of the most dramatic
of these sacrifices is exhibited by a carpenter ant from SE Asia. These ants act as walking bombs. There is a huge internal gland that occupies
much of their body that is filled with toxic chemicals. If one of these ants is hard pressed by a
rival ant or predator it contract some large abdominal muscles that bursts open
the abdomen violently (like a bomb) releasing the chemicals.
The availability or more significantly the limited
availability of food frequently is important in colony survival. As a consequence rival colonies frequently
develop strategies to maximize their collection of available food. There is a tiny fast moving ant in the deserts
of Arizona that utilizes toxic secretions to intimidate and confuse much large
honey ants (10 time their size) as they steal food from the larger ant colonies. In addition these tiny ants will frequently
prevent honey ants from leaving their nests by releasing toxic chemical down
the hole or nest entrance thus driving the former below ground. This of course allows the smaller species to
forage without competition from the honey ants.
Another form of nest entrance blocking is exhibited by a small ant species
in the southwestern deserts. In this
case they gather in mass around the nest entrance of their rivals and similarly
release toxic chemicals down the entrance.
However in addition they pick up pebbles, twigs and other small objects
and drop them down the vertical shaft entrance.
Possibly the most elaborate of all documented
aggressive strategies in social insects occurs in battles between the tiny woodland
ant and the imported fire ant. The fire
ants are deadly enemies of the woodland ants with colonies 100 times larger
than their tiny rivals. Even though fire
ants are much more powerful than the woodland ants both successfully survive in
the same area. The secret of woodland ant
survival evolves around a specialized soldier (major) and a three-stage
strategy to defend against fire ant attack.
These soldiers are equipped with huge heads that are equipped with large
sharp jaws provided with massive muscles.
These do not attempt to sting or spray their enemy with poisons (common
in many ants) but quite precisely use their mandible to snip off legs, heads
and other body parts. Unless attacked
the majors remain in the colony.
However, the minors regularly forage for food but are always on the
alert for scout fire ants that are looking for colonies to raid. If a woodland ant minor encounters a fire ant
soldier close to its colony a violent response is triggered. Once detected the minor rushes to the fire
ant in a mock attack but merely touches the potential invader in order to
acquire some of its odor. She then
quickly retreats toward her nest. As she
retreats she lays a pheromone trail by periodically touching her abdomen to the
ground. On her way back she briefly rushes
up to any other minor alerting them to the presence of the fire ant scout. Once in the nest soldiers plus many of the
minors are alerted to the presence of the invader scout (by its smell on the
minor worker) they subsequently rush in mass along the already establish
pheromone trail leading to the enemy.
Once found the soldier surrounds the fire ant and attack relentlessly
and are fully capable of destroying it due to their great superiority in
numbers. Of course the whole purpose is
to kill the fire ant scout before it can alert other fire ants in the area as
to the presence of a woodland ant colony.
Once accomplished the soldiers search the general area for any other
fire ant scouts.
If fire ants mount a full scale attack of a woodland
ant colony, the defenders have an alternate strategy. As fire ants arrive in
full force the entire force of woodland soldier ants are sent into the
battle. Soon the battle ground is
littered with the bodies of the smaller species plus a multitude of legs and
other body parts of the fire ants. As the
battle continues any woodland ant minors still present retreat to the nest. As
more and more fire ants arrive and the woodland ant soldiers are greatly
out-numbered they retreat, close ranks to form a dense protective perimeter
around their colony entrance. With the
impending doom that the fire ants will soon break through the protective
barrier and ravage, steal and consume the woodland ant’s eggs, larvae and pupae
the activity of the minors in the colonies is frantic but well programs. They gather the young in their mandibles and
sprint out though the colony entrance, through the battle field and beyond to
safety. The woodland ant soldiers remain
true to their programmed behavior and fight to the death. Once the fire ants
leave the now ravaged colony the minors return with their cargo of eggs, larvae
and pupae and reestablish colony life.
Over time new soldiers develop in the colony preparing for the
possibility of another raid. Such is the
life of ants!
Some ants survive by controlling the environment in
which they live. In the Amazon rain
forests there is a tremendous diversity of vegetation. If you walk through the forest no plant
typically dominates and you may not see any two plants of the same species
within hundreds of yards. One notable exception is the Cordia tree. On occasion you
will find a large stands of these trees with no other plants in the
vicinity. In addition these stands are
typically encircled by large barren strips of land. The reason for this phenomenon is the
presence of a small ant species that lives within the stems of these
trees. They are very protective killing
any plant feeding insects. They will
also swarm on and attack any larger animal venturing into the stand. In addition any other species of plants that
germinates with in the stand quickly shrivels and dies due to the ants stinging
and injecting venom into the terminal buds.
As might be expected the barren areas surrounding the stand of trees is
similarly cleared by the stinging of these ants. Of course the ants benefit from this
symbiotic relationship since they are provided by a safe bountiful location for
their nests. And of course the trees
benefit as they are provided with an endless competitively free environment in
which to expand their growth. People
living in the rain forest refer to the barren areas as the “devil’s garden” and
refrain from planting crops there.
Honey Ants. Ants vary
tremendously as to their food preferences, size and colony locations. The honey
ants are among some of the more interesting species. Normally they live in arid
desert regions of the world; their primary diet is honeydew, which they collect
from aphids and other homopterans. In such dry areas, honeydew-producing
insects are common during the rainy season only when host plants prevail.
Because in most areas this season only lasts a few months, honey ants have
developed a means of ‘storing’ honeydew from season to season. A special form
of worker called the replete, or reservoir ant, accomplishes this. These
repletes are fed huge amounts of honeydew; consequently, their abdomens stretch
to many times the normal size. Once fed, reservoir ants remain inactive and
store honeydew for many months. In many areas of the world, reservoir honey
ants are human’s food—they are collected and their abdomens are bitten off. The
stored honeydew gives them a candy-like taste.
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Honey Ants-Myrmecocystus Spp..
Worker media and
replete castes of honey ants. Image
courtesy Greg Hume at Wikepedia.
Colonies of these amazing insects
develop specialized workers, called repletes or honeypots, with tremendously
swollen abdomens for nectar storage. Some repletes also hoard water, fats and
body fluid from insect prey. The repletes ingorge on food that is collected
outside the nest and brought to them by normally-proportioned worker ants. Deep
in underground chambers, the repletes hang quietly in clusters, literally
imprisoned by their abdomens ballooned to the size of small grapes (Figure )!
Worldwide there are several very
different kinds of ants that exhibit extreme repletism; all are properly called
honey ants. One outstanding group; the genus Myrmecocystus, occurs
exclusively in western North America. Myrmecocystus contains a diverse
ensemblage of at least 28 closely related species, many of which are broadly
distributed. It follows that these honey ants are very common insects. Most
human residents or visitors to the American Southwest have probably strolled
atop a honey ant nest completely unaware of the treasure trove hidden below.
But those lucky enough to view repletes first hand can't help but want to find
out more about these astonishing creatures.
Honey ants are highly social insects. They live in
efficiently organized colonies or groups of cooperating individuals. Their
societies are matriarchal or female-dominated families. A typical honey ant
colony contains a single fertile queen and thousands of sterile female workers.
The queen is the mother of the colony and is specialized for egg production,
while the workers, the queen's daughters and hence all sisters, are responsible
for colony labor.
Worker honey
ants are polymorphic, meaning that they come in different sizes, ranging
ten-fold or more in body weight. This variation, in turn, permits more
effective task specialization. For example, the smallest workers, called
minims, tend to remain in the nest as nursemaids caring for the queen, the
developing brood (eggs, larvae and pupae) and the repletes. Medium and larger
size workers are more apt to be involved with nest excavation, food acquisition
and colony defense. The largest workers, called majors, are the individuals
most likely to develop into repletes. Honey ant colonies are coordinated
largely by pheromones, glandular secretions produced by the ants that function
as chemical signals. Pheromones regulate complex social behavior and broadly
serve to identify colony members, recruit nestmates to food sources, and elicit
alarm and defensive behaviors. For example, honey ant workers instantly
distinguish nestmates from intruders based on their smell (colony odor); the
former might be groomed and offered food while the latter would be attacked and
killed or driven from the nest.
Honey ant societies may also contain
numerous non-working reproductive forms, or winged males and virgin queens.
Winged forms, called alates, are produced when colony populations reach an
optimal size and become reproductively mature. Then, a portion of the brood
raised each year is converted into individuals designed to mate, disperse and
start new colonies. Mating flights typically are nocturnal or crepuscular, and
generally occur only once a year following the first heavy precipitation of the
summer rainy season.
The reproductive forms pour out of the
nest and swarm into the air, mating on the fly. Young queens take only one
mating flight; they store viable sperm long-term in a special organ, called a
spermatheca, which is then used for fertilizing eggs throughout the remainder
of their lives.
The males, their primary function
completed, die shortly after mating. The inseminated queens drop to the ground,
twist off their now useless wings, and scamper across the surface of the warm
wet ground, looking for a place to burrow. The vast majority of the queens fall
victim to a barrage of predators including birds, lizards, spiders and
especially, other ants. Surviving queens must be well below ground before the
rising sun relentlessly dries and bakes the surface. The queens seal themselves
inside humid, subterranean cavities and do not forage; rather, they rear their
first brood of tiny workers, called nanitics, relying solely on their stored
fat reserves and metabolized flight muscles. Colony growth is slow at first,
but soon rapidly accelerates as additional ants are added to the worker force.
Honey ant nests almost always have only
a single surface opening surrounded by a small accumulation of excavated
substrate. Each species has a characteristic nest entrance. For example, M.
mimicus builds a low sandy mound while M. mexicanus constructs a turret
of coarse gravel. Nest openings of the latter species are very distinctive and
not easily confused with those built by other kinds of ants in the area. The
amount of soil surrounding a honey ant nest entrance is deceptively small, for
the nest tunnels and chambers frequently extend deep into the ground, often
reaching several yards or more below the surface. Nests of M. mexicanus
have been studied in detail and have a surprisingly distinct and seemingly
adaptive architecture. The nests typically are built in hard rocky soil, and
consist of a subsurface labyrinth of tunnels and a vertical array of small
domed chambers interconnected by one narrow vertical passageway. The maze of
tunnels just below the surface probably serves as a staging area for foraging
parties and mating flights and as a site for brood incubation. The lower
chambers, deep enough to be within the level of permanent soil moisture, house
the queen, much of the worker population and the majority of repletes. The lone
interconnecting passage probably makes individual nest chambers easier to
defend or seal off from enemy invaders.
Honey ants are generalized scavengers and predators.
Sugary carbohydrates are needed for energy. The ants visit flowers and
extrafloral nectaries for the sweet rewards, and "milk" homopterans
like aphids and scale insects for their sugary exudations called honeydew. Once
engorged with liquid sugar, workers return to their nest to share with other
colony members.
Protein sources also are necessary, particularly for the
growing larvae. Foraging honey ants search for live or recently dead
invertebrates, predominantly arthropods; small soft-bodied insects like
termites and caterpillars are especially fair game. Individual workers head
homeward with pieces of food clasped within their mandibles, while groups of
workers may cooperate when retrieving large or struggling prey items.
Like all formicine ants, honey ants lack stingers:
rather, they spray fine droplets of formic acid from their abdominal tip. The
caustic acid is used, along with pinching mandibles, to help subdue
uncooperative prey or to deter colony enemies. Grappling with prey or facing
off against their foes, attacking honey ants spread and brace their legs,
rapidly curl their abdomens underneath pointing forward, aim and fire. Their
chemical weaponry is most effective against small targets; it is useful against
mammals or other large animals only if sprayed into highly sensitive tissues
like eyes or nostrils.
Given an abundance of sweet repletes, it
is not surprising that badgers and other desert creatures sometimes burrow into
and plunder honey ant nests. Even some honey ant colonies will raid one
another, stealing not only repletes but also brood, that when mature, is
"enslaved" as part of the pirating colony's worker force.
As recently as early this century,
various Native American tribes and Mexicans regularly excavated honey ant
colonies to obtain the savory morsels stockpiled therein. Sweet-toothed human
predators typically hold a replete's head and thorax with the fingers, bite off
or rupture the fragile abdomen, then suck its contents into the mouth. The
so-called "honey" tastes somewhat like molasses, while the ants'
bodies, being bitter, are discarded. Perhaps fortunately for honey ants, this
practice seems to have fallen by the wayside due to the advent of commercially
available candies. These not only taste better but are much less work to
procure.
Many social insects, notably honey bees and some
wasps, collect and store liquid sweets for later use. However, these insects
stow their food within the confines of their nest combs. Honey ants are unique
in using their own bodies as living storage vessels.
But why develop repletes? In arid regions, food and
water usually are obtainable only for very limited periods. But when available,
as during the brief summer rainy or growing season, these resources are present
in overwhelming abundance. Under favorable conditions, surplus food gathered by
the colony is fed to the repletes for long-term storage. Then, in times of
need, the food is regurgitated back to colony members.
While the formation of food-storing repletes seems
remarkable, it is merely an exaggerated form of typical ant behavior. Most ants
possess expandable abdominal crops (stomachs) for temporarily carrying liquid
food back to the nest. When solicited by a hungry nestmate, they regurgitate
this liquid and offer a small droplet held between their mandibles. Close
observation will reveal that the donor ant's abdomen shrinks as the recipient's
abdomen expands. Thus, the crop serves as a "communal stomach" and
repletism simply as extreme development of this expandable organ.
In the presence of excess food, repletes can develop
from any newly emerged worker, apparently before its exoskeleton and intersegmental
membranes harden and become less flexible. In young colonies, it is not
uncommon to find small workers serving as somewhat ineffective repletes, with
their tiny abdomens distended to the bursting point. However, on an individual
basis, major workers make the most efficient honeypots. Hundreds to a thousand
or more large repletes can be found in mature honey ant colonies, each
patiently hanging and waiting to serve up dinner when called upon by its
nestmates.
Argentine Ant. Linepithema humile.
.
Argentine Ant tending soft scale for
honeydew. Image courtesy Penarc.
Identification. The Argentine ant is a one node, small, shiny, brown
ant with only one size of worker. Workers are usually about 1/12 to 1/8
inch long. The queen ants are much larger, sometimes reaching 1/4 inch in
length. They nest outdoors under logs, concrete slabs, debris and
mulch. Argentine ants build very large colonies and can move
rapidly. During winter months, this ant will move indoors.
Biology. This ant is successful and hard to control because:
·
Different
Argentine ant colonies in a same general locale are not enemies. Even the
many queens in a single colony or separate colonies are friendly to each other.
·
Argentine
ants are not too "picky" when choosing a suitable site to infest or
colonize. They readily (as you will read about in move their nests during the changing seasons and other
conditions.
·
These pests
are omnivorous; they seem to never be in short supply of food.
·
Each colony of
Argentine ants contains a multitude of workers.
·
Each worker is
more courageous and harder worker than most ants. Creatures that attempt
to prey on Argentine ants are confronted with an army of stubborn bugs that
never runs from a fight!
·
The queens of
most ant species are usually egg-laying machines. The queen ant of
Argentines actually helps in the care, grooming and feeding of her young.
·
Most
species of ants mate and reproduce by swarming; the Argentine mates in the
colony, unexposed to the perils of birds, frogs, lizards, predator insects and
extreme weather conditions. A swarmer reproductive (as seen with fireants and carpenter ants) has about
1 chance in 1,000 of surviving and successfully reproducing. The
Argentine ant queen always succeeds!
Distribution. Originating
from Northern Argentina near the Paraná River and surrounding regions, the
Argentine ant now occurs in most regions with Mediterranean climates or with
mild winters and moderate to high humidity. Argentine ants are established in
at least 15 countries on six continents and many oceanic islands, including New
Zealand, Japan, and Hawaii. The global distribution of Argentine ants continues
to expand. Humans have been the primary factor in their spread, however, this
ant can also disperse into new areas without human influence. The Argentine ant
is widely distributed in California, with highest abundance in coastal areas,
along rivers, and in urban settings.
It was discovered by scientists two years ago that native Argentine ant
(in Argentina)colonies living in close proximity were territorial and
aggressive toward one another, literally tearing one another apart whenever
they came into contact. The puzzling question to the researchers was, Why
weren’t the introduced ants in California the same way? Why would an Argentine
ant from San Diego dropped into a colony in San Francisco be welcomed, while an
Argentine ant dropped into a colony two hundred meters away in its native
country be torn apart?
In search to the answer to that question the genetic
differences among the ants in Argentina were compared with those in various
parts of California, from San Diego to Ukiah. Using some of the same DNA
fingerprinting techniques employed by criminologists, it was discovered that
the native Argentine ants were twice as diverse as the native California ants,
explaining why the California ants regard individuals up and down the coast as
close kin, while those different nearby colonies in Argentina do not. They have
an innate ability to recognize other members of their colony based on how
genetically similar they are to themselves.
Basically the genes are similar among California ants because they are
descended from a relatively small founding population In essence, the super
colony that we see in California is in fact one big colony.
Damage. Because it
does not sting or bite the Argentine ant is not a direct threat to humans,
unlike harvester ants or fire ants. However since there is little competition
between opposing colonies of this species (one giant colony) this ant is the
dominant species in areas where it becomes establish. It is very aggressive toward other species of
ants and tends to out competes and replace other ants that are found in their
same general area. As a result the Argentine ant is by a long way the major
nuisance pest in urban areas, especially because of the availability of water.
This ant exists in back yards at high densities associated with landscape
features that provide favorable microclimates, such as potted plants and
walkway bricks or stones. They enter homes through cracks and other spaces, in
search of food or water.
Argentine
ants are also an economic threat because of their potential to tend plant pest
insects, such as mealybugs, scales, and aphids. In return for sweet honeydew
secretions from these plant feeding insects, ants provide protection from
natural enemies. Argentine ants may even move pests to better food sources or
more favorable microclimates to maximize honeydew production. This mutualism
can compromise management of pest insects by otherwise effective natural enemies,
through removal or intimidation of predators and parasitoid wasps, leading to
higher pest densities and greater plant damage than would occur in the absence
of Argentine ants. For example, parasitism rates of an important citrus pest,
the California red scale (Aonidiella
auranti), were reduced two- to five-fold in the presence of Argentine ants.
Control. There are
no known specific enemies of the Argentine ant. Therefore control is primarily
via chemical and cultural means. Broadcast spraying of insecticides is of
limited value because a substantial portion of Argentine ant colonies exist
below ground where insecticides are unable to penetrate. Poison bait stations
have proven effective at controlling Argentine ants in vineyards, though
prolonged deployment may be required for natural enemy-mediated reductions on
honeydew producing pests to become apparent. Control in homes and yards include
sanitation (e.g. removal of food scraps), closing points of entry to homes, and
removing landscaping features that promote favorable microclimates - especially
excess water sources.
Leaf-cutting Ants. These are commonly found in many New World
tropical areas. In such areas, columns of these ants frequently can be seen
crawling up the trunks of trees and cutting small discs from the leaves. In
some areas these insects are so common that they become major agricultural
pests.
Leaf
cutting ants carrying leaf discs.
Some of these ants exhibit polymorphism (different
form within a caste –in this case the workers) to an extreme. There are 4 different forms within the worker
caste, namely the minima, minors, media and maxima. The minima are the smallest
form of the adults and function to care for the brood (larvae and pupae) and
fungal gardens. Media workers forage for and carry the leaf discs deep into
their nests, where they are licked, cut into smaller pieces, dampened with an
anal secretion and finally formed into a bed of moist pulp. The newly formed
beds are then planted with fungi from established beds. As the fungus grows, it
is harvested and fed to the larvae. Most leaf cutting ants are quite particular
and typically cultivate and harvest only one species of fungus. Media workers
continuously ‘weed out’ any alien species of fungi that infest their gardens. It
is believed that a few species actually produce fungicidal substances from
their salivary glands, which chemically aid in the weeding process. In some
species, when the swarming queens leave the colony, they carry the strands of
fungi with them in pouches below their heads. Once new colonies are begun, the
strands are ‘planted’ to assure a new garden of the correct species of fungi. The maxima are the largest of the forms with
enlarged heads and protruding mandible.
These of course are the soldiers of the colony and function to protect
the colony against intruders.
In a few species of leaf-cutting ants, the minor caste
performs a rather specialized function. These smaller workers frequently
accompany the larger foraging leaf-gatherers; they do not assist in leaf
cutting; but ride back to the nest either on the leaf portion or on the thorax
of the media. Their sole function is to protect the media by snapping their
mandibles at a species of parasitic fly that attempts to lay eggs on the
media’s head.
Carpenter Ants. On
occasion, carpenter ants are confused with termites by the homeowner. These two
are easily distinguished by any of a number of characteristics. As in all ants,
the abdomen is connected to the thorax by a narrow waist, or petiole, while the
abdomen of a termite is broadly joined to the thorax. Also, in the winged
forms, a termite’s wings extend far beyond the tip of the abdomen and their
front and hind wings are of equal size and shape. In winged ants, the hind
wings are much smaller than the front wings and both rarely extend beyond the
tip of the abdomen. Many carpenter ants are large and typically black in color.
Unlike termites, carpenter ants do not eat wood and rarely cause damage to
structures. In California, their nests may occur inside the wooden parts of
homes, but in such cases they usually have occupied abandoned drywood termite
nests. Carpenter ants eat a variety of things, including other insects.
A common carpenter ant.
Army Ants. The most spectacular and well-known
ants are the legionary, or army, ants of the humid tropical forests. These ants
do not construct nests, but form temporary clusters called bivouacs in the
shelter of fallen trees or in other partially exposed situations. The workers
form a solid mass up to a yard wide, which consists of layer after layer of
individuals hooked together by their tarsal claws. The queen, larvae, pupae,
and eggs are located in the center of this mass.
An army ant, not considered as dangerous
to humans as commonly believed.
The night is passed in a tight cluster, but at the
first sign of light the cluster dissipates and hoards of workers fan out from
the bivouac in all directions. Soon, one or more columns form and begin to
search for food. The workers lay down a pheromone trail for others to follow
while the soldiers guard the perimeter of the trail. Workers form numerous
columns; changing positions behind the advancing hoards of ants—flushing out
large numbers of prey (arthropods, small reptiles and rodents). The prey is
stung, killed and transported to the rear as food for the larvae. At the end of
the day the cluster is reformed. When the food supply is depleted around the
area of the bivouac, the colony relocates.
Some colonies of army ants may number as high as one
million individuals. Because of the spectacular size of their colonies and
‘raiding’ nature of these insects, they have been used repeatedly by the motion
picture industry. Actually army ants pose no threat to humans or other large
animals.
The authors recently had the opportunity to observe
army ant behavior in Costa Rica. One morning we were walking down a dirt road
with several students collecting insects. Collecting was not that good but
suddenly hoards of insects, spiders and even a few scorpions and lizards
started pouring out from the underbrush across the road we were on. After a few
moments of excellent collecting, we decided to investigate the reason for this
windfall. And, as you might suspect, there was a column of army ants moving
through a gully to the side of the road. Of course all the animals in its path
were attempting to flee. On the following evening a column of army ants raided the
students' cabin. The students were not awakened, but the following morning they
were very disappointed to see that the army ants had stolen most of the several
thousand insects they had collected and mounted on pins over the past week.
Shortly thereafter, I decided to test the reports that army ants pose no threat
to humans. There was a column moving through our pension grounds--so I placed
my foot directly in their path. They merely ignored this obstacle and marched
over and around it.
While the army ants are primarily found in the New
World tropics the driver ants are found in the tropics of Africa. Both types are very similar as far as their
behavior and biology is concerned. One
distinct difference is that while large colonies of army ants may number one
million colonies of driver ants can reach 200 million. With such huge numbers they present more of a
threat to humans and other animals.
There have been human deaths recorded from the raids of these critters
(mostly infants). In these cases death
has typically occurred from suffocation as a result of the ants entering and
filling the lungs.
The mating behavior of these ants is especially
strange. The males are to drawn to the
foraging columns supposedly looking for a mate.
Instead of finding a queen the sterile workers quickly swarm the males
and immediately tear their wings off.
Then they carry them off and basically imprison them until a potential
new queen is available.
Bullet Ants. This ant is
primarily found in rainforests ranging from Nicaragua to Paraguay and Australia. This huge (1 inch) beast is called the bullet
ant because its sting feels like being shot by a bullet. On the Schmidt Sting Index bullet ants rate
as the number one most painful sting found in the arthropods. When defending their nest they swarm out,
release a strong odor and stridulate an audible sound (said to sound like a
shriek) and then grab and impale their intruder. In Central-South America they are referred to
as the 24-hour ant, referring to the pain described as “of burning, throbbing,
all consuming pain” that may last a day or more.
A one-inch Costa
Rican bullet ant.
As with many other arthropods bullet ants play a ceremonial
role in some tribes of the rainforests. The Satere-Mawe people of Brazil use
this ant in the right of passage of boys into manhood. In this case live bullet
ants are woven into a sleeve made of leaves with the stingers pointing inward. Once the sleeve is place on the arm the goal
is to leave it on for 10 minutes without crying due to the stings. When finished the boys arms are temporarily paralyzed
and they may shake uncontrollably for days.
To fully complete the initiation, however, the boys must go through this
ordeal a total of 20 times over a several month period or years.
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Harvester Ants. These (Pogonomyrmex spp.) are commonly thought
as the large red or black ants that form rather large nests in open fields,
schoolyards, along railroad tracks, alleys or other similar situations. Of the 23 species that occur in the United States
22 occur west of the Mississippi River. Beside their large size and color these
ants can be distinguished by fringes of long curved hairs on the back,
underside margin of the head. These
hairs are used to clean the ant’s antennae and legs, carry water and remove
sand during excavation of their nests. The nests are typically quite large
consisting of one or more holes surrounded by a low flat crater (up to 8 inches
across). This crater in turn is
surrounded by a rather large vegetation free area
A
black harvester ant.
Harvester ants feed primarily on seed. In agricultural areas they are considered
beneficial as they remove weed seeds from crops. The main reason they are found
along railroad tracks is due the grain that is lost during transportation.
Harvester ants readily sting but
typically are not aggressive unless defending the nest. If disturbed they will swarm from the nest and
readily sting. Their venom is extremely powerful resulting in considerable pain
that may last for several days.
Harvester ant venom is the most toxic venom found in arthropods although
there is considerably less than in black widows and consequently the sting of
the ant is much less dangerous than the bite of the spider.
Fire Ants. There are
many species of fire ants in the United States, but the most serious pests are
4 in the genus Solenopsis: the red imported fire ant, the black imported
fire ant, the southern fire ant, and the fire ant. Distinguishing between
imported and native species of fire ants is difficult, even for experts.
Identification usually requires 40 or more randomly collected worker ants for
study.
Black Imported Fire Ant. The black imported fire ant, Solenopsis
richteri, is very similar to the red imported fire ant. Its current
distribution is limited to a small area of northern Mississippi and Alabama. It
may be displaced from established habitats by the red fire ant. Scientists have long thought that the black
and red fire ants were 2 distinct species. Recently it has been discovered that
hybrids of these ants produce viable offspring, and some scientists now wonder
whether they are simply 2 races of the same species, varying in color and
perhaps behavior.
Southern Fire Ant. The
southern fire ant, Solenopsis xyloni, is a native species that occurs
from North Carolina south to northern Florida, along the Gulf Coast and west to
California. In California it occurs in the lower altitudes from Southern
California up through Sacramento but is seldom found along the coast in central
to northern California. This is probably
our most common native species of ant but its distribution is greatly retarded
when the Argentine ant is present.
However in areas where the Argentine ant is controlled, populations of
this species rapidly return.
Colonies may be observed as mounds or
more commonly may be constructed under the cover of stones, boards, and other
objects or at the base of plants. These ants also nest in wood or the masonry
of houses, especially around heat sources such as fireplaces. Nests often
consist of loose soil with many craters scattered over 2 to 4 square feet. In
dry areas nests may be along streams, arroyos, and other shaded locations where
soil moisture is high. Southern fire ants usually swarm in late spring or
summer.
The workers are very sensitive to
vibrations or jarring. If their nest is
stepped on they will rush out and sting the feet and legs of the intruder. Individual reaction to their venom is quite
variable depending on allergic reaction.
There is a least one case of a human infant death due to mass stinging
of this species.
This species is practically omnivorous
feeding on a variety of materials including honeydew, meat, seeds, fruit, nuts,
cereal and cereal products, grease and butter and dead and living insects. It
can be quite detrimental to agriculture foraging for seeds from seed beds,
girdling nursery stock, and consuming fruits and vegetables. In addition these ants will remove insulation
from wiring and occasionally gnaws on a variety of fabrics.
Fire Ant. The fire ant, Solenopsis geminata, is
a native species sometimes called the tropical fire ant. It ranges from South
Carolina to Florida and west to Texas. It is very similar to the southern fire
ant except its head is much larger and the petiole node is higher and
narrower. This species usually nests in
mounds constructed around clumps of vegetation, but may also nest under objects
or in rotting wood.
Red Imported Fire
Ant. The red and black imported
fire ants were first reported in the United States in 1929. It is thought that they came to the port in
some soil used as ballast in the bottom of a cargo ship. Since this introduction the black fire ant
has not spread as rapidly as the red imported species. By 1953 (first official USDA survey) the red
imported fire ant had spread to over 100 counties in 10 states. Today it is prevalent throughout the
southeastern US and has moved into Texas, New Mexico. Arizona and California.
Natural movement of fire
ants is limited to mating flight or by rafting during period of flooding. However, the rapid movement of these species
across the South and westward is mainly associated with human activity. In this case the initial spread of these
ants in the southeastern US was thought to be due to movement of sod and potted
ornamental plants. This
inadvertent movement of S. invicta and S. richteri was noted by
the U.S. Department of Agriculture in 1953 when a direct link was established
between commercial plant nurseries and the spread of imported fire ants. In
response to mounting public pressure, the U.S. Congress appropriated $2.4
million in 1957 for control and eradication efforts. As part of an overall plan
quarantine was imposed to retard or prevent the artificial dissemination of
these now notorious pests. On May 6th 1958, regulations governing the movement
of nursery stock, grass sod and some other items were instituted through the
Federal Quarantine 301.81. By that time, however, imported fire ants had moved
into 8 southern states. This spread, although slowed considerably by federal
regulations and climatic conditions, continues even today. In recent years,
isolated infestations of imported fire ants have been found as far west as New
Mexico, Arizona California and as far north as Kansas and Maryland. In the case of California it is thought that
the spread of these ants into this state was due to movement of bee hives as
most initial infestations were found in around orchards and other situations
where bees were moved into these areas for crop pollination. Based on USDA prediction these ants have a
potential of even expanding the spread throughout much of the United States.
.
Current and potential distribution of imported
red fire ant. Image courtesy of USDA.
Biology
Adult
fire ants (Genus Solenopisis) are
characterized by the presence of a ten-segmented antennae, two-segmented
antennal club and two-segmented waste that joins the thorax to the abdomen
which is typically darker than the rest of the body. Species identification is somewhat more
difficult due to hybridization between the 2 "native" species as well
as between the 2 imported species.
Diagram
of diagnostic characteristics of red imported fire ant.
A mature colony of fire ants typically consists of 4
main stages: egg, larva, pupa, and adults.
Since these are true social insect there is a caste system with
different shaped and sized adults that carry out different function within the
colony. These adult forms include the
polymorphic workers, winged males, winged females and one or more reproductive
queens. The egg, larval, and pupal stages (Figure 3) occur within the
underground nest and are only seen when nests are disturbed or when they are
being carried to a different location by workers (Figure 4). The eggs are small
but can be seen with the unaided eye. They hatch into the grub-like legless larvae
that are fed by the workers. Ant larvae in general are legless, carrot shaped
with a well-developed unpigmented head capsule and are typically hooked at the
head end. The larvae will grow and molt (shed their exoskeleton) 3 times prior
to molting into the pupae, which are similar in appearance to the adults except
that their legs and antennae are held tightly against the body. As with the
larvae the pupae lack pigmentation, especially in the early instars. As they mature they begin to turn
darker. As discussed in honeybees, the
function of the polymorphic workers is determined primarily by age (and to a
much lesser degree by size). Younger workers typically care for and feed the
brood while middle-aged workers maintain and protect the colony. The oldest
workers forage for food.
Figure 3. Egg, larval and pupal stage of fire ants.
Image courtesy of USDA Archives.
Figure 4. Worker fire ants carrying larva for
relocation. Image courtesy of USDA,
Calif. Dept Agriculture.
The alates, or winged reproductives
(Figure 5), are most abundant in the late spring and early summer, but can be
found at any time of the year. The males are decidedly smaller than the
females, glossy black and have a smaller head. Although both winged males and
females can be found in the same colony, as a general rule one form will be
dominant. It is possible that this functions to increase the chances of one sex
mating with another from a different colony. Most colonies in a given area
typically swarm on nuptial flights at the same time. This benefits the species
and insures mixing of the gene pool. It
is well-documented that inbreeding is generally detrimental to a given species.
Figure 5. A winged reproductive of the red imported
fire ant. Image courtesy of USDA
Archives.
Mating
flights most often occur at mid-morning 1 or 2 days following a rainfall if the
temperature is above 22°C and the wind is light. At this time a virgin female flies into a
cloud of congregating males and mates in the air. The male subsequently dies while the female
seeks a location to start a new colony. Once located, she breaks off her wings
and excavates a brood chamber approximately 1 to 2 inches below ground. The new queen subsequently deposits a few
dozen eggs which hatch in a little over a week. The queen does not forage but
feeds the first generation of larvae from nutrients obtained from her fat
reserves and by dissolving her no longer needed wing muscles. The larvae obtain
the nutrients by trophollaxisis (exchange of alimentary fluids) or from sterile
eggs she has produced for that purpose.
The entire life cycle is completed in 3 to 4 weeks.
The initial generation of adult worker (minims) are
relatively small due to a limited amount of nutrients available from the
queen. Once developed these worker open
up the brood chamber and begin to forage for available food. Soon another
generation of larger adult workers has developed and the colony begins to grow.
Workers start to emerge daily and within 6 months the colony population
approaches several thousand and an above ground mound is visible. The
polymorphic (poly in Latin means many and morph means form) nature of the
worker becomes more apparent. The largest workers in the colony (majors) can be
as much as 10 times the size of the smallest workers (media). The queen lives
up to 7 years and produces an average of 1600 eggs per day. At maturity, a
monogynous (one queen) fire ant colony can consist of over 250,000 ants. As discussed above some fire ant colonies
have only one queen per nest while others can have many queens and are called
polygynous colonies. The polygynous colony may be more difficult to control
because all the queens must be killed to prevent the colony from surviving.
Polygynous colonies frequently expand by "budding"; i.e., some of the
queens and workers break off from the parent colony and start a new mound nearby. This process in polygynous colonies can
accounts for much higher mound density which sometimes approaching 1,000 mounds
per acre.
Different sized worker adults. Image courtesy of USDA Archives.
One of
the identifying characteristics of an imported red fire ant colony is the earthen
nest or mound. This mound is a cone-shaped dome with a hard crust. They
averages 1 ˝ feet in diameter and 8-inches in height. In heavy clay soils they
can exceed 3-feet in height and 4 1/2 feet diameter. There are usually no
external openings in the mound; but tunnels a few inches below the surface
tunnels radiate several feet from the mound allowing foraging workers access to
the colony. These mounds serves several functions: They act as a flight platform for nuptial
flights and to raise the colony above ground in excessively wet soil while
protecting it above ground from intruders and rain. They also serve as a
passive solar collector to supply warmth to the colony during the cold winter
months.
Mound of red imported fire
ant. Image courtesy of USDA Archives.
In
areas with hot, dry summers these mounds may not be maintained or may not be
formed at all. In a dark, protected site
with sufficient moisture and an adequate supply of food, fire ants will nest in
a wide variety of locations (e.g. rotten logs, walls of buildings, under
sidewalks and roads, in automobiles, in dried cow manure).
Economic Impact
Fire
ants are omnivorous, feeding on almost any plant or animal material; although
dead and living insects seem to be their preferred food. In rural habitats,
they have a major impact on ground nesting animals (birds, reptiles, mammals).
Studies have shown that once established in a new area there is typically a
minimum of a two-fold reduction in the populations of field mice, snakes,
turtles and other vertebrates and a maximum of a total elimination of some
species. Fire ants also feed on plants
attacking young saplings and seedlings, destroying buds and developing fruits
and have been shown to feed on the seeds of over a hundred species of native
wildflowers and grasses.
Damage to plants is increased during periods of drought as fire ants
seek alternate water sources. In fields where drip irrigation is used, these
insects build their mounds over the emitters reducing or blocking the flow of
water to crops. In some cases, actual physical destruction of microsprinkler
assemblies has occurred. Finally, the mere presence of fire ants on plants and
within the field will deter hand-harvesting of crops.
As an urban pest, imported fire ants cause many of the same problems
experienced in rural areas. In addition
they nest within the walls of homes and offices. Colonies are established under sidewalks and
roadways frequently resulting in complete collapse of sections of these
structures if the nests are eventually abandoned. The presence of fire ants can
deter outdoor activities in yards, parks and school grounds. Home invasions can
threaten small children and the elderly. House invasions are especially
prevalent during periods of heavy precipitation and flooding. Fire ant colonies
have been found inside automobiles, trucks and recreation vehicles resulting in
traffic accidents caused by fire ants stinging the drivers. Imported fire ants
are attracted by electrical currents and have caused considerable damage to
heat pumps, air conditioners, telephone junction boxes, transformers, traffic
lights, and gasoline pumps.
Because of their reputation people fear fire ants. In some areas playgrounds,
parks, and picnic areas are rarely used because of the presence of fire ants.
In campsites of state and national parks in fire ant infested areas, it is
often difficult to put up or take down a tent without being stung by angry
ants.
Stings. Fire ants are best known for their
behavior of stinging, frequently in mass.
If a nest is disturbed hundreds if not thousands of ants will quickly
emerge and attack the intruder. This occurs so quickly and in mass that is not
uncommon to have hundreds on the victim before the first sting is felt. To make
matters even worse a single fire ant can sting repeatedly and will continue to
do so even after their venom sac has been depleted. Once reaching the victim
the ant will typically attach with its mandibles to the skin and then insert
its stinger. Subsequently it will rotate
it abdomen and repeatedly sting using the attached head as a pivot. The result is a circle of several stings
from the same ant.
Initially, the sting(s) result in a
localized intense burning sensation (hence the name "fire" ant).
Within a day or two a white pustule forms at the sting site (Figure 8). Pustule
formation occurs only with the red and black imported fire ant and not the
southern fire ant or fire ant. There is a possibility of secondary infection
and scarring if the wounds are not kept clean or if they are continually picked
at or scratched (Figure 9). As with any other hymenopterous stings, there are a
few individuals who are hypersensitive to the venom and can react quite
strongly and be severely affected.
Symptoms in these cases can include chest pains, nausea, dizziness,
shock or, in rare cases, lapsing into coma.
In cases of an allergic reaction, even a single sting can lead to a
potentially serious condition called anaphylactic shock. There are recorded
cases of human death resulting from fire ant stings but these are rare.
Pustular formation for sting of red imported fire ant. Image courtesy of USDA Archives.
Figure 9. Secondary infection of
sting from red imported fire ant. Image
courtesy of USDA Archives.
Individuals with disabilities,
reduced feeling in their feet and legs or reduced mobility, are at greater risk
from serious stinging incidents and the incidence of resulting medical problems
may be even greater. Large numbers of ants can sting and even overcome victims
before they can safely escape. There was a recent case where fire ants entered
a room of an elderly gentleman in a retirement hospital and basically stung him
to death. In his case he was unable to
escape their attack.
Individuals who are known to be
allergic to fire ant stings should seek professional advice from a physician or
allergist, especially if they are in situations where they might be exposed to
these pests. There are emergency treatment kits that are available (by
prescription) for individuals who are sensitive to their sting. Fortunately,
relatively few deaths from fire ant stings have been documented, especially
when compared to deaths from bee and wasp stings. Victims stung to death by
fire ants often were not able to escape, sustained large numbers of stings, and
suffered allergic reactions to the venom.
There are basically two methods of fire
ant control, namely individual mound treatment and broadcast treatment. Before attempting either, it is advisable to
check with regulatory agencies as the availability and use of different
chemicals for either method may vary from state to state. In addition, in many cases free control by
state governmental agencies of these pests is available.
Individual Mound Treatments. Treating
individual fire ant mounds can be time consuming, but it is generally the most
effective method of control. Once treated it will take anywhere from a few
hours to a few weeks before total elimination of a colony depending on the
product used, time of the year and size of the mound. Treatment is usually most
effective in the spring with the key being to treat all the mounds in the
area. If control is not complete,
reinfestation of an area can take place in less than a year. There are several different methods that can
be used to treat individual mounds.
Insecticides-One of the
more commonly used methods is drenching mounds with a high volume of diluted
contact pesticide. As with any treatment, it is extremely
important to follow label directions not only to attain maximum effect, but to
maximize safety of the application and avoid potential illegal consequences. In most cases the mounds and surrounding
areas are wetted thoroughly but gently with the drench. Subsequently the mound
is broken open and the insecticide is poured directly into the tunnels. Mound drenches are most effective after rains
when the ground is wet and the ants have moved up into the drier soil in the
mound. During excessively dry weather, effectiveness of the treatment may be
enhanced by soaking the soil around the mound with water before treatment. One
problem with this technique is that the queen may be too deep to be reached
with the drench. This may be especially true if the colony is disturbed prior
to an application. In this case the
workers may move the queen deeper into the colony in order to avoid a potential
threat.
Granular formulations are also available
for individual mound treatment. In this
case once the recommend dose is applied to the mound it should be watered
thoroughly in order to reach the worker ants and queen that occur deeper in the
colony. The dissolved granules must come into direct contact with the ants to
have any effect. As in mound drenches, care must be taken not to disturb the
colony prior to application.
A few insecticides are marketed as injectants. In
this case they may be injected using a "termite rig" with a
soil injector tip, a standard 1-3 gallon compressed air sprayer with a fire
ant injector tip, or a special aerosol soil injector system. The mound is injected
in a circular pattern, usually at 3 to 10 points. A new product combines
insecticide treatment with high temperature vapors to increase
penetration.
Fumigants are readily available in most states for fire ant control. These are
usually more effective than surface applications or mound drenches but are also
more expensive and can be dangerous if not handled properly.
Depending on
the state a number of fire ant baits are available. These can be used for
treating individual mounds or for broadcast treatment of larger areas. The bait
should be uniformly applied around the mound 0.3 to 1.0 meters away and not on
the mound itself. Baits are much slower acting than the control methods listed
above but are generally safer, cheaper and more effective in the long run.
Water - The use of
boiling water has been examined on several different occasions resulting in
varying degrees of success. In one experiment over a 50% of treated mound were
eliminated by pouring approximately 3 gallon of hot water directly into the
mound. The use of steam produced by a
steam generator produced similar results.
Regardless both techniques are far less effective the use of drenches,
fumigants, granular formulation or baits are
cumbersome in the field are not practical when dealing with large
populations of these pests. Area wide flooding with water has not proven to be
effective, impractical in most situations and can led to spreading of the
population due to the rafting ability of these insects.
Broadcast Treatments - A number of fire ant
baits (Figure 10) are commercially available for broadcast treatments (again
depending on the state). Baits are composed of an inert carrier-attractant
(corn carrier and soybean oil) and toxicant. The active ingredient (either a
slow-acting insecticide or an insect growth regulator) is incorporated into the
oil. These baits can be applied either by a hand operated granular fertilizer
spreader or larger equipment. Once foragers find bait they carry it back to the
nest, ingest it and begin feeding other ants in the nest. Because the active ingredients are slow
acting, they are spread around the nest before the desired effect. This formulation and means of application has
a number of advantages. Unlike individual mound treatments, colonies need not
be "located" in order for them to be treated and as a result this
method is less time intensive and consequently less expensive than individual
mound treatments. On the other hand
broad cast treatment has the potential of affecting non-target organisms. It is also slow acting and the effectiveness
of the bait is greatly reduced when they come in contact with water from rain,
irrigation or other sources. Finally
baits are only effective during those times of the year or temperatures when
the ants are readily foraging. Generally
speaking it is advisable to only use this type of treatment in areas where
there is little or no human traffic. If
broadcast treatment is used in such an area, a good choice is growth regulator
bait, which poses much less risks to non-target species. For example,
fenoxycarb bait has been shown to be very effective for suppression of fire ant
populations when applied in one application over a wide area.
Figure
10. A corn- based bait used for control
of the red imported fire ant. Image
courtesy of USDA Archives.
Figure
11. A tractor driven granular
applicator. Image courtesy of USDA
Archives.