CHAPTER
4
Arachnids-Spiders
Included
in this order are all the spiders. Spiders have 4 pair of legs, no
antennae, and from 1 to 4 pairs of eyes. As in all arachnids, the first
pair of appendages behind the mouth is called chelicerae and appears as hollow
fangs. Poison glands are connected to the fangs and are used to subdue
prey. Spiders feed by external digestion.
When a spider bites its prey, it injects venom and a digestive
enzyme. The function of the digestive
enzyme is to dissolve the internal parts of its prey so the spiders can
subsequently “suck it dry” with its hollow fangs. Most species of spiders are relatively harmless
to humans. In fact the fangs of most
spiders are too small and weak to penetrate thicker human skin. A few spiders
are potentially harmful to humans and will be discussed.
Black
Widows and Related Species. The black widow spider is
found in every state of the country and there are similar species throughout
much of the world. There are 5 or 6 species of widow spiders belonging to
the genus Lactrodectus in the United States, each being marked slightly
different and all of which have a fairly toxic bite. There are 2 species
that are restricted to southern Florida, namely the brown widow and the red
widow.
Western
Black Widow, Lactrodectus Hesperus.
This is the species most
commonly associated with the name black widow in the Western United
States.
A female
black widow, Lactrodectus hesperus. Right image courtesy James Gathaway CDC Photo Library.
Only the female of
the species is dangerous and is named after the practice of her killing the
male immediately after copulation. In actuality the female is usually
pretty well fed and more times than not the male escapes before being
consumed. The males are several times
smaller than the females and brownish in color with pearly markings on the top
of the abdomen. As with many spiders,
the male’s pedipalps are club-shaped and used to transfer sperm to the female.
A male black widow. Image Courtesy of Marjory Moody.
The immature
females are often brown and striped with colored markings. All stages
(except the youngest spiderlings) have a red marking on the underside of the
abdomen. This red marking serves as a warning coloration to any potential
predator. Bright colors in most animals
serve the same function, advertising the fact that this animal is potentially
dangerous and to stay away. The black
widow female hangs upside down in her web thus making this marking clearly
visible.
The female
is nocturnal and lies in wait on the web for passing prey. The male
typically is not found in the web but hunts either for food or a female. The web is characteristically asymmetrical in
shape, strong, and produces a crackling sound when probed. The female can
produce from 1 to 10 marble shaped white egg sacs in the spring. These eggs hatch within 10 days or so and the
young spiderlings remain inside the sac until after their first molt. The young spiderlings typically leave the sac
about 30 days after when the eggs are first laid. There may be as many as 200 spiderlings in
each sac. Once emerged they feed on
mites and small insects. The life cycle
is completed in 4 to 6 months. Black
widows typically live about a year. These spiders can be found in many situations
but common environment requisites include high humidity, food and dark
protected locations.
As
with other spiders, black widows balloon or parachute as spiderlings. Ballooning is a term used for the mechanical kiting that many, especially smaller species of spiders, as well as certain mites and some caterpillars use to disperse through the air. Many
small spiders use silk to lift themselves off a surface or use the silk as an
anchor in mid air. Biologists
also apply the term "balloon silk" to the threads that mechanically
lift and drag systems.
A spider or spiderling after hatching will climb as high as it can. The
spider then stands on raised legs with its abdomen pointed upwards. This is
known as "tiptoeing". After
that, it starts releasing several silk threads from its abdomen into the air,
which automatically form a triangular shaped parachute. The spider can then let itself be
carried away by updrafts of winds, where even the slightest of breeze will do. Most rides will end a few meters
later, or a spider can be taken up into a jet stream, which
depends on its mass, posture, the convection air current, drag of silk and parachute to float and
travel high up into the upper atmosphere.
Many sailors have reported spiders have
been caught in their ship's sails, over 1600 km from land. They have even been
detected in atmospheric data balloons collecting air samples at slightly less
than 5 km (16000 ft) above sea level. Apparently it is the most common way
for spiders to invade isolated islands and mountaintops. Spiderlings are known to survive
without food travelling in air currents of jet streams for 25 days or longer.
It is generally thought that most
spiders heavier than 1 mg are not likely to use ballooning. Also,
because many individuals die during ballooning, it is more unlikely that adults
will do it than spiderlings. Adult females of several social Stegodyphus species (S. dumicola and S. mimosarum), weighing
more than 100 mg and with a body size of up to 14 mm, have however
been observed ballooning using rising thermals on hot days without wind. These
spiders use tens to hundreds of silk strands, which formed a triangular sheet
with a length and width of about 1 m.
With black widow
and other species spiderlings as temperatures cool and wind turbulence
decreases at night, these spiderlings float back to earth. If they reach the prescribed environmental
conditions they survive-if not they die.
In actuality very few young spiderlings survive to adulthood; however,
because the female can produce as many as 2,000 or more spiderlings during her
lifetime, only 2 needs to survive, replace the parents and perpetuate the
species.
These spiders are
not typically aggressive except in defense of the egg sacs. The
fangs of a black widow are quite small and incapable of penetrating thick
skin. Consequently a black widow must
bite you on the soft parts of your body.
The bite of this spider is rather painless at first; however, a systemic
effect soon develops because of a strong neurotoxin. The toxin of a black
widow is said to be 15 times as toxic as that of a rattlesnake. However, there is much less toxin so the bite
is not nearly as bad as that of the snake.
Pain begins after 1 to 3 hours and continues for 24 to 48 hours.
Pain often starts in the lymph nodes (groin, armpits) and spreads to the lower
back. The stomach muscles develop severe cramps due to rigid
contractions. The skin feels clammy; blood pressure drops, profuse
sweating, and nausea are other symptoms that may develop. Additional
symptoms include facial muscle spasms, breathing difficulties and
convulsions. The mortality rate of the bite of an adult female black
widow in humans is approximately 5% of untreated cases. Most deaths occur
in young children (more venom per body mass) or individuals who are already in
poor health.
The most common
location where black widow bites occur in Southern California is outdoor
bathrooms. Right under the toilet seat
it is dark, humid and abounds with flies.
So in the springtime when the female is guarding her egg sacs and one
wiggles her web with soft body parts, it can be quite surprising (ouch!).
There is an
antivenin available for bites. This is
not always given as it can only be taken once.
Frequently hospital patients are given Demerol or something else for the
pain if the bite doesn’t seem to be too serious or life threatening. The
antivenin is quite effective; however, it is not always advisable to use on all
patients as some may develop an allergic reaction.
The black widow
antivenin is produced by a fairly complicated procedure. There are a number of small companies that
raise black widows by the thousands.
Applying a mild electrical shock stimulates the spider to exude a tiny
drop of venom from each chelicera.
Subsequently, this venom is collected with small capillary tubes and
saved. The venom from each company is
pooled twice a year in the U.S. to make the antivenin. This is accomplished by
injecting small amounts of the venom into horses that already possess a degree
of natural immunity to this toxin. After
a few weeks when the horses have developed even more immunity as a result of
exposure to the venom, serum is condensed from their blood to make the
antivenin
As previously
mentioned occasionally individuals treated with antivenin will develop allergic
reactions. One such reaction is to
develop hives and other symptoms when eating beef. Apparently at least some of the protein in
beef is the same or similar to that in horse blood serum. As consequent an allergic reaction unfolds in
some cases when beef is consumed.
Control of Black Widows and Other Spiders. Typically pesticide control of spiders is difficult
unless you actually see the spider and are able to spray it. There are various
insecticides available in retail outlets labeled for spider control, including
pyrethrins, resmethrin, allethrin, or combinations of these products. If you
spray a spider, it will be killed only if the spray lands directly on it; the
spray residual does not have a long-lasting effect. This means a spider can
walk over a sprayed surface a few days (and in many cases, a few hours) after
treatment and not be affected. Control by spraying is only temporary unless
accompanied by housekeeping. It is just as easy and much less toxic to crush
the spider with a rolled up newspaper or your shoe or to vacuum it up. Sticky
traps offer a pesticide free way to remove spiders from your home as long as
you can place the traps where pets and curious children can’t tamper with them.
Sorptive dusts containing amorphous silica gel (silica aerogel) and pyrethrins,
which can be applied by professional pest control applicators only, may be
useful in certain indoor situations. Particles of the dust affect the outer
covering of spiders (and also insects) that have crawled over a treated
surface, causing them to dry out. When applied as a dust-like film and left in
place, a sorptive dust provides permanent protection against spiders. The dust
is most advantageously used in cracks and crevices and in attics, wall voids,
and other enclosed or unused places.
Other
Worldwide Black Widow
Brown
Widow Spider-Latrodectus geometricus. This spider is also commonly known as the brown
widow, grey
widow, brown
button spider, or geometric button spider.
The brown widow is found in parts of the southeastern, south and southwestern United States (including Florida, Alabama, California, Oklahoma, Nevada, Louisiana, Mississippi, Georgia, South Carolina, Tennessee, Arizona, New Mexico and Texas); as well as in parts of Australia, South Africa and Cyprus. It has recently received considerable attention and has been
accidentally introduced Orange County, California and other parts of the
country. The origin of this species is
uncertain, as specimens were independently discovered in both Africa and in the Americas. They are usually found
around buildings in tropical areas.
L. geometricus is generally lighter in color than the black widow species—the color can range from tan to
dark brown to black, with shades of grey also possible. Like the black widow
species in the United States, L.
geometricus has a prominent
"hourglass" marking on the underside of the abdomen; however, the
brown widow's hourglass is usually a vivid orange or a yellowish color. Unlike
the black widow geometricus has
a black-and-white "geometric" pattern on the dorsal side of its
abdomen. Although the Latin name comes from this pattern, a spider's coloring
can and does darken over time and the pattern may become obscured.
Brown widows can be located by finding
their egg sacks, which are easily identifiable. They resemble a sandspur, having pointed projections all over, and they are
sometimes described as "spiky" in appearance. Eggs hatch in
approximately 20 days.
Like all Latrodectus species, L. geometricus has medically significant neurotoxic venom. Dr.
G.B. Edwards, a University of Florida arachnologist claims that brown widow
venom is twice as potent as the black widow venom, but is usually confined to
the bite area and surrounding tissue, as opposed to the black widow. Other
sources say that the brown widow is less venomous than L. mactans. Regardless, people
who have been bitten typically describe the experience as very painful and
extreme care should be taken when working or playing in the areas they inhabit.
Brown Widow Females with an Asymmetrical and
Spiked Surface Egg Sac.
Latrodectus mactans, Southern Black Widow. This species is well known for the
distinctive black and red coloring and for the fact that she will occasionally
eat her mate after reproduction. The highly venomous species is native to the United States of America and Mexico. The female black widow's venom is particularly
harmful to humans (males almost never bite humans). The injection of venom from
these species is a comparatively dangerous or lethal bite.
Latrodectus mactans was first described by Johan Christian Fabricius in 1775, placing it in the genus Aranea.
The
species is closely related to Latrodectus hesperus (western black widow) and Latrodectus variolus (northern black widow). Members of the
three species are often confused with the genus Steatoda, the False
Black Widows. Prior to 1970, when the current taxonomic divisions for North American black widows were set forth, all three varieties
were classified as a single species, L.
mactans. As a result, there exist numerous references which claim that
"black widow" (without any geographic modifier) applies to L. mactans alone. Common usage of the term
"black widow" makes no distinction between the three species.
The mature female is around 1.5 in
(38 mm) long and 0.25 inches in diameter. She is shiny and black in color,
with a red marking in the shape of an hourglass on the ventral (under) side
of her very rounded abdomen. There is much variation in female size, particularly
in egg-carrying (gravid) females. The abdomen of a gravid female can be more
than 0.5 inch in diameter. Many female widows also have an orange or red patch
just above the spinnerets on the top of the abdomen. The male is either black,
or closer to the appearance of the juveniles in color, and is much smaller with
a body of less than 1/4 inch. Juveniles have a distinctly different appearance
to the adults; the abdomen is grayish to black with white stripes running
across it and is spotted with yellow and orange.
Southern Black Widow Male with Knobbed
Pedipalps. Image Courtesy Joseph Berber,
Bugwood.
The southern widow is primarily found in
(and is indigenous to) the southeastern United States, ranging from Florida to New York, and west
to Texas, Oklahoma, Arizona, and. The northern black widow (L. variolus) is found
primarily in the northeastern United States and southeastern Canada, though its range overlaps that of L. mactans. In Canada, black
widows range in the southern parts of British Columbia, Alberta, Manitoba and
Ontario.
Latrodectus mactans, along with Latrodectrus hesperus and Latrodectus geometricus (the "brown widow spider"), is
established in the Hawaiian Islands (USA). One pathway of entry into Hawaii for
at least one of these black widow species is imported produce (which is also considered an important
potential pathway for widow spiders elsewhere.
When a male is mature, he spins a sperm
web, deposits semen on it, and charges his palpi with the sperm. Black widow spiders
reproduce sexually when the male inserts his palpus into the female's
spermathecal openings. The female deposits her eggs in a globular silken
container in which they remain camouflaged and guarded. A female black widow
spider can produce four to nine egg sacs in one summer, each containing about
100-400 eggs. Usually, eggs incubate for twenty to thirty days. Rarely do more
than a hundred survive through this process. On average, thirty will survive
through the first molting, because of cannibalism, lack of
food, or lack of proper shelter. It takes two to four months for black widow
spiders to mature enough to breed, however full maturation typically takes six
to nine months. The females can live for up to five years, while a male's
lifespan is much shorter. The female, on occasion, eats the male after mating. Latrodectus mactans is the only black widow species for
which this form of sexual cannibalism has been
observed in the wild. The lifespan
depends upon environment, with shelter being the greatest determining factor
and food the second greatest. Males
that escape being consumed by the females can go on to fertilize other females.
It is a widely held misconception that females eat males after every mating.
Black widow spiders typically prey on a
variety of insects, but occasionally they do feed on woodlice, diplopods, chilopods and other arachnids. When the prey is entangled by the web, Latrodectus mactan quickly
comes out of its retreat, wraps the prey securely in its strong web, then bites
and envenoms its prey. The venom takes about ten minutes to take effect; in the
meantime, the prey is held tightly by the spider. When movements of the prey
cease, digestive enzymes are released into the wound. The black widow spider
then carries its prey back to its retreat before feeding.
There are
various parasites and predators of widow spiders in North America, though
apparently none of these have ever been evaluated in terms of augmentation
programs for improved bio control. Parasites
of the egg sacs include the flightless scelionid wasp Baeus latrodecti, and
members of the chloropid fly genus Pseudogaurax. Predators
of the adult spiders include a few wasps, most notably the blue mud dauber, Chalybion californicum, and the spider wasp Tastiotenia festiva. Other
species will occasionally and opportunistically including Mantis or Centipede also can take widows as prey, but these
two are general predators and do not significantly reduce population of these
spiders.
Although
these spiders are not especially large, their venom is extremely potent.
Compared to many other species of spiders, their chelicerae are not very large or powerful. In the
case of a mature female, the hollow, needle shaped part of each chelicera, the part
that penetrates the skin, is approximately 1.0 millimeters (about 0.04 in)
long, long enough to inject the venom to a point where it can be harmful. The
males, being much smaller, inject far less venom with smaller chelicerae. The
actual amount injected, even by a mature female, is very small in physical
volume. When this small amount of venom is diffused throughout the body of a
healthy, mature human, it usually does not amount to a fatal dose (though it
can produce the very unpleasant symptoms of latrodectism). Deaths in
healthy adults from Latrodectus bites are relatively rare in terms of
the number of bites per thousand people. Sixty-three deaths were reported in
the United States between 1950 and 1959[16]. On the
other hand, the geographical range of the widow spiders is very great. As a
result, far more people are exposed, worldwide, to widow bites than to bites of
more dangerous spiders, so the highest number of deaths worldwide is caused by
members of their genus. Widow spiders have more potent venom than most spiders,
and prior to the development of antivenin, 5%F of reported bites resulted in
fatalities. The venom can cause a swelling up to 15 cm. Improvements in
plumbing have greatly reduced the incidence of bites and fatalities in areas
where outdoor privies have been replaced by flush toilets.
Latrodectus tredecimguttatus-Mediterranean Black Widow or Steppe Spider. This is a
species of widow spiders in the genus Latrodectus. It is
commonly found throughout the Mediterranean region, ranging
from Spain to southwest
and central Asia, hence the name. Specimens from central Asia are also
known by the binomial name Latrodectus
lugubris; that name, however, is considered obsolete, though it is still
commonly found in the literature. Many consider this spider a Latrodectus mactans subspecies. L. tredecimguttatus bears different names in different
regions. For example, in Southern France it is called l'araignée malmignatte.
Throughout the Eastern Slavic region (part of Balkans), the name karakurt is most often applied. A direct
translation from Turkmen language suggests that kara stands for "black", while kurt might mean "insect" or
"bug".
It is black in color, similar to most other
widow species, and is identified by the thirteen spots which are found on its
dorsal abdomen (the species name is Latin for
"thirteen spots"). These spots are usually red in color, but may also
be yellow or orange. It is otherwise similar to other species in the genus Latrodectus. The Mediterranean
widow primarily lives in steppes and other grasslands, and can be a significant
problem in areas where grain is harvested by hand.
Female
(Left) and Male (Right) Mediterranean Black Widows. Images Courtesy of K. Korlevic.
Like all Latrodectus species, L. tredecimguttatus has a painful bite that is fatal in
rare cases. There are many reports of Ukrainian Farm Workers receiving bites
while working in fields. In Kazakhstan, there are
reports of this species biting and killing camels (probably no true). It is now believed that this
species is the cause, often falsely attributed to the wolf spider (Lycosa tarantula).
Redback Spider,
Latrodectus
hasselti. The female redback has a round body about the size
of a large pea, with long, slender legs. The body is a deep black color
(occasionally brownish), often containing an obvious orange to red longitudinal
stripe on the upper abdomen. The stripe is sometimes broken or looks like small
red dots. On the underside of the abdomen there is an "hourglass"
shaped red/orange spot. Juvenile spiders have additional white markings on the
abdomen. The male redback is three to four millimeters long and is light brown
in color with white markings on the upper side of the abdomen and a pale
hour-glass marking on the underside.
Female Redback Spider.
Image Courtesy Peter Chew.
As with other members of this genus the
redback web is a disorganized, irregular tangle of fine but strong silk. The
rear portion of the web forms a funnel-like retreat area where the spider and
egg sacs are found. This area has vertical, sticky catching threads that run to
ground attachments.
Redbacks usually prey on insects but can capture
larger animals that become entangled in the web including king crickets, trapdoor
spiders, and small lizards. Commonly
prey stealing occurs where larger females take food items stored in other
spiders' webs. Most commonly,
ants stray into the web.
Female Redback Capturing Cicada Several
Times its Size. Image Courtesy Peter
Chew.
Male spiders mature in 37 to 167 days
(average in about 90 days). Females mature in 60 to 325 days (average in about
four months). Males live for up to 6 or 7 months while female may live for
between 2 and 3 years. Even without food spiders may survive for an average of
100 days.
The redback spider is one of only two
animals to date where the male has been found to actively assist the female in sexual cannibalism. In the process of mating, the much smaller male
somersaults to place his abdomen over the female's mouthparts. In about 2 out
of 3 cases, the female consumes the male while mating continues. Males who are
not eaten die soon after mating.
Males who sacrifice themselves during
mating present two advantages over males who do not. The first is that males
who are eaten are able to copulate for a longer period and thus fertilize more
eggs. The second is that females who have eaten a male are more likely to
reject subsequent males.
Some redback males have been observed
utilizing an alternative tactic that also ensures that more of their genetic
material is passed on. Juvenile female redbacks who are nearing their final
molting and adulthood have fully formed reproductive organs but lack openings
in the exoskeleton that allow access to the organs. Males will bite through the
exoskeleton and deliver sperm to the organs without performing the somersault
seen in males mating with adult females. The females then molt within a few
days and deliver a normal clutch of eggs.
Once the female has mated, she can store
sperm and use it over a period of up to two years to lay several batches of
eggs. A female spider may lay eggs every 25 to 30 days. A single female normally
deposits between 40 and 300 eggs in each sac but can lay up to 5000 eggs. The
eggs hatch 13 to 15 days after being laid. Young redback spiders leave the
maternal web by being carried on the wind. The spider extends its abdomen high
in the air and produces a droplet of silk. The liquid silk is drawn out into a
long thread that, when long enough, carries the spider away. Eventually the
silken thread will adhere to an object where the young spider will establish
its own web.
Its origins are uncertain, and it may
have been spread by human activities during the 19th century. Redback spiders
are now found in all but the most inhospitable environments in Australia. The
redback spider is commonly found in close proximity to human residences. Webs
are usually built in dry, sheltered sites, such as among rocks, in logs,
shrubs, old tires, sheds, outhouses, children's toys or under rubbish or
litter.
Media in Japan have reported the
discovery of redback spiders in Osaka, Japan within a hundred kilometers of Kansai International Airport. It was speculated that they arrived in
Japan by "hitching" a ride on the outside of airliners, or carried in
cargoes of wood chips. In 2008,
redback spiders were found in Fukuoka, Japan. Over 700 have been found near the
container terminal in Hakata Bay, Fukuoka city. Warning signs about redback
spiders have been posted in parks around the city as Japan has had no venomous
spider before now.
Redback spiders are also found in small
colonies in areas of New Zealand. These spiders were imported on Australian
hardwood poles used for electric power and telephone. They are found around Central Otago in the South Island and New Plymouth in the North Island.
Venom is produced by glands in the cephalothorax,
and expelled venom travels through paired ducts from the cephalothorax, exiting
through the tip of the spider's hollow fangs. The venom of the redback spider
is thought to be similar to other Latrodectus spiders and contains a number of high molecular
weight proteins, one of which, alpha-latrotoxin (aneurotoxin), is active
in humans. In vertebrates alpha-latrotoxin produces its effect
through destabilization of cell membranes and degranulation of nerve terminals
resulting in the release of neuro-transmitters; it causes uncontrolled release
of the neurotransmitters acetylcholine, norephedrine, and GABA. The release of these neurotransmitters leads to the
clinical manifestations of envenomation.
Redback spider bites rarely cause
significant morbidity, and deaths
are even rarer. On Australian record only 14 deaths from redbacks have been
recorded. A significant
proportion of bites will not result in envenomation or any symptoms developing.
It is believed that thousands of people are bitten each year across Australia,
although only about 20% of bite victims require treatment. Children and the elderly or those with
serious medical conditions are at much higher risk of severe side-effects and
death resulting from a bite. No deaths have been reported since the
introduction of antivenom in 1956.
The larger female spider is responsible
for almost all cases of redback spider bites in humans. The smaller male spider
was thought to be unable to inject venom into a human; however, male bites have
occurred. The rarity of male bites is probably due to smaller size and
proportionally smaller fangs rather than the male being incapable of biting or
lacking venom of potency similar to the female's. Cases have shown that the
male bite usually only produces short-lived, mild pain.
Most bites occur in the warmer months
between December and April and in the afternoon or evening. As the female redback is slow moving
and rarely leaves its web, bites generally occur as a result of a person
placing a hand or other body part too close to the web, such as reaching into
dark holes or wall cavities. But bites can occur wherever the spider may gain
access, such as when putting on shoes or dressing.
Bites from redback spiders produce a
syndrome known as latrodectism. The
symptoms are similar to bites from other Latrodectus spiders. The syndrome is generally
characterized by extreme pain and severe sweating. Initially the bite may be
painful but sometimes only feels like a pin prick or mild burning sensation.
Within an hour victims generally develop more severe local pain with local
sweating and sometimes pilo-erection (goose
bumps). Pain, swelling and redness spread proximally from the site. Systemic
envenoming is heralded by swollen or tender regional lymph nodes; associated
features include malaise, nausea, vomiting, abdominal or chest pain,
generalized sweating, headache, fever, hypertension and tremor. Rare
complications include seizure, coma, pulmonary edema, respiratory failure or
localized skin infection. Severe pain
can persist for over 24 hours after being bitten.
Medical advice should be sought after
being bitten by a redback spider. Usually this requires observation in or near
a medical facility for six hours from time of the bite. Treatment is based on the severity of
the bite; patients with localized pain, swelling and redness usually do not
require any specific treatment apart from applying ice and routine analgesics. In more
severe bites the definitive treatment consists of administering redback antivenom. Antivenom
will usually give immediate relief to symptoms of systemic envenoming.
Antivenom is indicated in anyone
suffering symptoms consistent with Latrodectus envenoming. Particular indications for
using antivenom are:
§
Pain and swelling spreading proximally from site
§
Chest pain
§
Abdominal pain
§
Unusual sweating
Currently it is recommended that this
antivenom be given intramuscularly rather than intravenously, although
some have suggested that IM antivenom is not as effective as IV antivenom. Adverse reactions to redback antivenom
are rare and antivenom may be
effective for up to 3 months after a bite. Doses
are the same for both children and adults.
Latrodectus katipo, the Katipo. This is an endangered species of spider native to New Zealand. A member
of the genus Latrodectus, it is
related to the Australian redback spider, and the North American black widow spiders. The species is venomous to humans, capable of
delivering a comparatively dangerous spider bite. Katipo is
a Māori name and means "night-stinger. They
range throughout most of coastal New Zealand, but are not found at the
southernmost regions. Spinning an irregular tangled web amongst dune plants or
other debris, they feed mainly on ground dwelling insects.
The katipo is a small to medium-sized
spider. The mature
female has a body size of about 0.3 inch with a leg span of up to
1.3 inches. It has a large black globular abdomen, about the size of a garden pea, with slender legs and a white-bordered orange or red
stripe on its back that runs from the uppermost surface of the abdomen back to
the spinnerets. The dark velvet-black abdomen is described as satin
or silky in appearance, rather than being shiny. The underside of the abdomen
is black and has a red patch or partial red hourglass-shaped
marking. It has mainly black legs with the extremities changing to brown.
Adult males and juveniles are quite
different in appearance to the female. They are smaller in size, being about
one sixth the size of an adult female. Juveniles have a brown carapace, with a
predominantly white abdomen which has a series of red-orange diamonds running
along the dorsal region bordered on either side by irregular black lines. Males
retain this coloration into adulthood.
Female Adult Katipo. Image Courtesy of http://www.flickr.com/people/27388205@N00
The katipo is restricted to a highly
specialized habitat and is only found near the seashore living among sand dunes. They
generally reside on the landward side of dunes closest to the coast where they
are most sheltered from storms and sand
movement. They can sometimes be associated with dunes several kilometers from
the sea when these dunes extend inland for long distances.
Like other theridiid spiders, the web is a disorganized,
irregular tangle of fine textured silk. It is hammock-shaped and is made up of
opaque yellowish-white silk. The
web consists of a broad base with many supporting threads above and below,
including a number of sticky guy lines anchored to debris in the sand. A
cone-shaped retreat is built in the lower part of the web, although the katipo can normally be
found near the main body of the web. The plants it builds its web in
provide support and shelter for the nest.
The katipo is endemic to New Zealand. In the North Island it is found along the West Coast from Wellington to North Cape. On the east coast of the North Island it occurs
irregularly, however, it is abundant on Great Barrier Island. In the South Island it is found in coastal regions south to Dunedin on the east
coast and south to Greymouth on the west coast. This southern limit is due to the
katipo needing temperatures higher than about 17 °C (63 °F) to be
maintained during the development of their eggs, explaining why they are not
found in the southern areas of New Zealand where it is typically colder than
this.
The male wanders as an adult and in
August or September goes looking for the females' webs to mate. The male will enter the female's web and vibrate the
silk as he approaches her. The female is usually aggressive at first and will
chase the male from the web. The courtship process consists of the male
bobbing, plucking and tweaking the web along with periods of cautious approach
and being chased by the female. Eventually, when she becomes docile and allows
him to approach, the male will then approach the female as she hangs quietly
upside down in the web. The male moves onto her ventral abdomen,
tapping her rapidly until she moves to align his abdomen above hers. He then
inserts his palps one at a time, leaving the female
between each insertion. Copulation occurs over 10 to 30 minutes. After mating, the male retreats to groom, which is
performed by running his palps and legs through his fangs and wiping them over
his body. The male is not eaten by the female unlike some other widow spiders.
The females lay their eggs in November or December. The eggs are round, about the size of
a mustard seed, and are a
transparent, purple-red. They are held together in a cream-colored, round, ball
shaped egg sac which is about 12 mm (0.47 in)
in diameter. The female constructs five or six egg sacs over the next three to
four weeks. Each egg sac contains about 70 to 90 fertilized eggs. The egg sacs
are hung in the center of the spider’s web and the female spins more silk over
them. Over time the exterior of
the egg sac may become covered with sand. After
six weeks of incubation, during January and February, the spiderlings hatch.
The young spiders then
disperse from the web. At present, little is known about the dispersal mechanism
that the spiderlings use to move away from the nest. In one study, observing
spiders over 24 hours, 28% used a ballooning method, which is where the young
spiders use heat currents to carry themselves away from the nest suspended by a
single web strand. While the majority, 61%, used a bridging method where the
spiderling uses its silk to move to nearby plants, and 11% still remained in
the nest. The young spiderlings reach full maturity the following spring.
The katipo is an endangered species and has
recently become threatened with extinction. It is estimated that there are only a
few thousand katipo left in about 50 areas in the North Island and eight in the
South Island. A
number of reasons have contributed to its decline; the major factors appear to
be loss of habitat and
declining quality of the remaining habitat. Human interference with their natural habitat has been occurring for over a century
following European settlement. Coastal dune modification resulting from agriculture, forestry, or urban development along with recreational activities like
the use of beach buggies, off road vehicles,
beach horse riding and driftwood collection have destroyed
or changed areas where katipo lives. The introduction of many invasive
exotic plants has also contributed to the decline of suitable habitat.
The katipo has medically significant venom in humans, although bites are rare. The incidence of bites is low as it is
a shy, non-aggressive spider. Their narrow range,
diminishing population, and human awareness of where they live means
interaction between humans and the spider is minimal.] The katipo, as with other black widows,
will only bite as a last resort; if molested, the spider will usually fold up
into a ball and drop to the ground or retreat to the nearest cover. If the
threat continues, the spider may throw out silk against the interference. When
restrained in any way or held against skin, such as if tangled up in clothing,
the spider will then bite defensively. However, if the female is with an egg
sac it will remain close by it and sometimes move offensively to bite any threat.
Bites from Katipo spiders produce a
syndrome known as latrodectism. The venoms of all Latrodectus spiders are thought to contain similar
components with the neurotoxin α-latrotoxin
the main agent responsible. Most bites are caused by female
spiders; the male katipo was considered too small to cause systemic envenoming
in humans. However,
bites from male redback spiders have been reported suggesting male Latrodectus spiders can cause envenoming in
humans. Although bites by male spiders are much rarer than those by females,
perhaps due to their smaller jaws rather than lacking venom of similar potency
to females or being unable to administer an effective bite. Māori legends recall many deaths
and there were reports of severe katipo bites in 19th or early 20th century
records, however, the only two reported fatalities were recorded in the 18th
century. No other
fatalities from spider bites have ever been reported in New Zealand.
The clinical
features of latrodectism are similar for all species of Latrodectus spiders and are generally
characterized by extreme pain. Initially,
the bite may be painful, but sometimes only feels like a pin prick or mild
burning sensation. Within an hour victims generally develop more severe local
pain with local sweating and sometimes piloerection (goosebumps). Pain, swelling and
redness spread proximally from the site. Less commonly,
systemic envenoming is heralded by swollen or tender regional lymph nodes; associated
features include malaise, nausea,
vomiting, abdominal or chest pain, generalized
sweating, headache, fever, hypertension and tremor. Rare complications include seizure, coma, pulmonary
edema, respiratory
failure or localized
skin infection. The
duration of effects can range from a few hours to days, with severe pain
persisting for over 24 hours after being bitten in some cases.
Treatment consists of observation in a medical facility
for six hours from the time of the bite. Patients with localized pain, swelling
and redness usually do not require any specific treatment apart from applying ice
and routine analgesics. In more
severe bites, antivenom can be
given.
Recluse, Violin
or Fiddleback Spiders.
This group of
spiders is known as the fiddleback, recluse or violin spiders. Loxoceles
reclusa or the brown recluse spider is commonly found in the central and
south-central states and Loxoceles laeta or the Chilean brown
spider (also known as the South American violin) was found in Los Angeles a
number of years ago but recent identifications are non-existent. There is also considerable controversy as to
if the brown recluse spider still exists in California. The medical community annually reports
treating many bites from the recluse spider. However, spider experts claim this
spider no longer exists in California. Because little is known about the effect
of the bite of many spider species, it is quite possible that the medically
treated cases are not due to the recluse but any of a number of other
spiders. This is especially possible
when allergic reactions are considered.
Brown Recluse Spider or Violin Spider, Loxosceles recluse. This is a well-known member of the
family Sicariidae (formerly placed in a family
"Loxoscelidae").
Brown recluse
spiders are usually between Ľ in and ľ inch, but may grow larger.
They may be brown, gray, or a deep yellow color and usually have markings on
the dorsal side of their cephalothorax, with a
black line coming from it that looks like a violin with the neck of the violin pointing
to the rear of the spider, resulting in the nicknames fiddleback spider, brown fiddler or violin spider.
Since the violin pattern
is not diagnostic, and other spiders may have similar markings (i.e. spiders and pirate
spiders), for purposes of identification it is far more
important to examine the eyes. Differing from most spiders, which have eight
eyes, recluse spiders have six eyes arranged in pairs with one median pair and two lateral pairs. Only a few other spiders have
three pairs of eyes arranged in this way, and recluses can be distinguished
from these as there are no coloration patterns on the abdomen or legs, which
lack spines. The abdomen is
covered with fine short hairs. The leg joints may appear to be a slightly
lighter color. Other identifying characteristics: Stance on a flat surface usually is with all
legs well extended unless alarmed, when it may withdraw its forward two legs
straight rearward into a defensive position, withdraw its rear pair of legs
into a position for lunging forward, and raise the pedipalps. Movement at virtually any speed is an evenly
paced gait with legs extended, stopping naturally when renewing its internal hydraulic blood pressure (that like most
spiders is required to renew strength in the legs); it then continues at a
steady pace until again it needs to renew its blood pressure. When threatened
it usually flees, seemingly to avoid a conflict, and if detained may further
avoid contact with fast horizontal rotating movements.
Relative Sized
of Adult Recluse and Eye Pattern. Left
Image Courtesy of BR-recluse-guy. Right Mattb.
Recluse
spiders build irregular webs that frequently include a shelter consisting of
disorderly threads. These spiders frequently build their webs in woodpiles and
sheds, closets, beds, garages, plenum, cellars and
other places that are dry and generally undisturbed. They seem to favor
cardboard when dwelling in human residences, possibly because it mimics the
rotting tree bark which they inhabit naturally. They also have been encountered
in shoes, inside dressers, in bed sheets of infrequently used beds, in stacks
or piles of clothes, behind baseboards and pictures, and near sources of warmth
when ambient temperatures are lower than usual. Human-recluse contact often is
when such isolated spaces are disturbed and the spider feels threatened. Unlike
most web weavers, they leave these webs at night to hunt. Males will move
around more when hunting, while the female spiders tend to remain nearer to
their webs.
The brown recluse spider
is native to the United States from the southern Midwest south to the Gulf of Mexico. The
native range lies roughly south of a line from southeastern Nebraska through southern Iowa, Illinois, and Indiana to southwestern Ohio. In the
southern states, it is native from central Texas to western Georgia north of Virginia and very common in the Northwest
particularly Washington State. A
related species, the brown violin
spider (Loxosceles rufescens), is found
in Hawaii. Despite
many rumors to the contrary, the brown recluse spider has not established
itself in California. There are
other species of Loxosceles native to the southwestern part of
the United States, including California, that may resemble the brown recluse,
but these species have never been documented as physiologically significant.
Symptoms. As
indicated by its name, this
species is rarely aggressive. Actual brown recluse bites are rare. The spider
usually bites only when pressed against the skin, such as when tangled up
within clothes, bath towels, or in bedding. Many human victims of brown recluse
bites report having been bitten after putting on clothes that had not recently
been worn or disturbed. In fact,
many wounds that are necrotic and diagnosed as brown recluse bites can actually
be methicillin-resistant
Staphylococcus aureus (MRSA) or simple staphylococcus infections.
Other causes include skin cancer, Lyme disease, and other infected insect bites
and skin lesions. Brown recluse bites may produce a range of symptoms known as loxoscelism. There are two types of loxoscelism: cutaneous (skin) and systemic
(viscerocutaneous).
Most bites
are minor with no necrosis. However, a
small number of bites produce severe dermo-necrotic lesions, and, sometimes,
severe systemic symptoms. These symptoms can include organ damage, and
occasionally even death; most fatalities are in children under 7 or those with a weaker than normal immune
system. (For a comparison of the toxicity of several kinds of spider bites, see
the list of spiders
having medically significant venom.)
A minority of brown recluse spider bites form a
necrotizing ulcer that destroys soft tissue and may
take months to heal, leaving deep scars. The damaged
tissue will become gangrenous and eventually slough away. The
initial bite frequently cannot be felt and there may be no pain, but over time
the wound may grow to as large as 10 inches in extreme cases. Bites
usually become painful and itchy within 2 to 8 hours; pain and other local
effects worsen 12 to 36 hours after the bite with the necrosis developing over
the next few days.
Serious
systemic effects may occur before this time, as the venom spreads throughout
the body in minutes. Mild symptoms include nausea, vomiting, fever, rashes, and muscle
and joint pain. Rarely more severe symptoms occur including hemolysis, thrombocytopenia, and disseminated
intravascular coagulation. Debilitated
patients, the elderly, and children may be more susceptible to systemic
loxoscelism. Deaths have been reported for both the brown recluse and the
related South American species L.
laeta and L. intermedia. Other recluse
species such as the desert recluse (found in the desert southwestern United
States) are reported to have caused necrotic bite wounds, though only rarely.
Numerous other spiders have been
associated with necrotic bites in the medical literature. A partial list
includes the hobo spider and the yellow sac
spiders. However, the bites from these spiders are not known
to produce the severe symptoms that often follow from a recluse spider bite,
and the level of danger posed by each has been called into question. So far, no known necrotoxins have been
isolated from the venom of any of these spiders, and some arachnologists have disputed the accuracy of many
spider identifications carried out by bite victims, family members, medical
responders, and other non-experts in arachnology. There have been several
studies questioning danger posed by some of these spiders. In these studies,
scientists examined case studies of bites in which the spider in question was
positively identified by an expert, and found that the incidence of necrotic
injury diminished significantly when "questionable" identifications
were excluded from the sample set.
Treatment.
First aid involves the application of an ice pack to control inflammation, the
application of aloe vera to soothe and help control the pain,
and prompt medical care. If it can be easily captured, the spider should be
brought with the patient in a clear, tightly closed container so it may be
identified. There is no established treatment for necrosis. Routine
treatment should include elevation and immobilization of the affected limb,
application of ice, local wound care, and tetanus prophylaxis. Many other
therapies have been used with varying degrees of success including hyperbaric
oxygen, dapsone, antihistamines (e.g., cyproheptadine), antibiotics, dextran, glucocorticoids, vasodilators, heparin, nitroglycerin, shock, curettage, surgical
excision, and antivenom. None
of these treatments have been subjected to randomized
controlled trials to
conclusively show benefit. In almost all cases, bites are self-limited and
typically heal without any medical intervention.
It is important to seek medical treatment if a brown
recluse bite is suspected, as in the rare cases of necrosis the effects can
quickly spread, particularly when the venom reaches a blood vessel. Cases of
brown recluse venom traveling along a limb through a vein or artery are rare,
but the resulting mortification of the tissue can affect an area as large as
several inches, to the extreme of requiring excising of the wound.
Dapsone is commonly used in the USA and Brazil for the treatment of necrosis. In presumed cases of recluse bites,
dapsone is often used effectively, but controlled clinical trials do not
demonstrate similar effectiveness; however,
dapsone may be effective at treating many "spider bites" because many
such cases are actually misdiagnosed microbial infections. There have been conflicting reports
about its efficacy and some have suggested it should no longer be used
routinely, if at all.
Wound infection is rare.
Antibiotics are not recommended unless there is a credible diagnosis of
infection. Studies have shown surgical intervention is ineffective and may
worsen outcome. Excision may delay wound healing, cause abscesses, and lead to
objectionable scarring.
Anecdotal
evidence suggests benefit can be gained with
the application of nitroglycerin patches. The brown recluse
venom is a vasoconstrictor, and nitroglycerin causes vasodilation, allowing the venom to be diluted into the bloodstream,
and fresh blood to flow to the wound. Theoretically this prevents necrosis, as
vasoconstriction may contribute to necrosis. However, one scientific animal
study found no benefit in preventing necrosis, with results showing it
increased inflammation and it caused symptoms of systemic envenoming. The
authors concluded the results of the study did not support the use of topical
nitroglycerin in brown recluse envenoming.
Antivenom,
available in South America for the venom of other species of recluse spiders,
appears to be the most promising therapy. However, antivenoms are most
effective if given early and because of the painless bite patients do not often
present until 24 or more hours after the event, possibly limiting the effect of
this intervention.]
It is
estimated that 80% of reported brown recluse bites may be misdiagnosed. The
misdiagnosis of a wound as a brown recluse bite could delay proper treatment of
serious diseases. There is now an ELISA-based test
for brown recluse venom that can determine if a wound is a brown recluse bite,
although it is not commercially available and not in routine use.
There are numerous documented
infectious and noninfectious conditions (including pyoderma gangrenosum, bacterial
infections by Streptococcus, herpes, diabetic
ulcer, fungal infections, chemical burns, toxicodendron dermatitis, squamous cell
carcinoma, localized vasculitis, syphilis, toxic
epidermal necrolysis, sporotrichosis, and Lyme disease) that
produce wounds that have been initially misdiagnosed as recluse bites by
medical professionals; many of these conditions are far more common and more
likely to be the source of mysterious necrotic wounds, even in areas where
recluses actually occur.
Reported
cases of bites occur primarily in Arkansas, Texas, Kansas, Missouri, Colorado, Nebraska and Oklahoma. There have
been many reports of brown recluse bites in California (and elsewhere outside the range of
the brown recluse); however the brown recluse is not found in California (though a few related species may be
found there, none of which has been shown to bite humans). To date, the reports
of bites from areas outside of the spider's native range have been either
unverified, or—if verified—specimens moved by travelers or commerce. Occasional
spiders have been intercepted in various locations where they have no known
established populations;Arizona, California, Colorado, Florida, Maine, Minnesota, New Jersey, Mexico, New York, North
Carolina, Wyoming and Tamaulipas
(Mexico), which indicates that these spiders may
indeed be transported fairly easily, though the lack of established populations
well outside the natural range also indicates that such movement does not lead
to colonization of new areas. Many arachnologists believe that many bites
attributed to the brown recluse in the West Coast are not spider bites at all, or
possibly instead the bites of other spider species; for example, the bite of
the hobo spider has been reported to produce similar
symptoms, and is found in the northwestern United
States and southern British
Columbia. However, the toxicity of the hobo spider has been
called into question as bites have not been proven to cause necrosis, and the
spider is not considered a problem in Europe. In addition, published work has shown
that tick-induced Lyme disease rashes are often misidentified as
brown recluse spider bites.
A recent
article in National Geographic News exemplifies how common it is to mistakenly
blame brown recluse bites on a number of other maladies. “Many diagnoses of brown
recluse spider bites come from areas apparently outside of the brown recluse's
habitat. Brown recluse spiders are found mostly in the central and southern
U.S., an area that includes Texas, Arkansas, Missouri, Kentucky, and Tennessee,
parts of Illinois, Indiana, and Georgia. Brown recluse spiders also inhabit the
states bordering the Gulf of Mexico. Yet Vetter (a UCR spider expert) has
fielded reports of brown recluse bites from Wisconsin, New York, even Alaska
and Canada. In virtually every case, systematic searches in those places have
turned up no brown recluse spiders. In one analysis, Vetter counted 188 reports
of brown recluse bites in three years in California, Oregon, Washington, and
Colorado. But only 15 brown recluse spiders have ever been found in those four
states. "These bite diagnoses are everywhere, and yet no one can find the
spider," Vetter said. "Show me the spider."
Even where
brown recluses do live, people overestimate their risk, Vetter said. In one
recent case in Kansas, a family of four collected more than 2,000 brown recluse
spiders in their house during a six-month period. The family found spiders on
the paper towel rack, crawling up the stairs, and lurking in piles of laundry.
"There were four people living in that house for six years," said
Vetter, who wrote about the case in the November issue of the Journal of Medical Entomology."Guess
how many bites? None."
Vetter and
colleagues have recently embarked on a project to census brown recluse spiders
in northern Illinois and southern Iowa. Similar studies elsewhere should
provide doctors and the public a better understanding of brown recluse
spiders."These spiders are dangerous and they can cause nasty
wounds," Vetter said, "but the perception of the brown recluse as a
serious health threat is overstated."
Control. The desert recluse is the only Californian
recluse of concern and a minor one at that (or the West Coast States as far as
that is concerned). After verifying that you do have desert recluses in your
home or workplace, there are steps you can take to reduce encounters with them
that are similar for reducing encounters with spiders in general. The most
important precaution is to remove and reduce trash and rubbish from your
property, such as woodpiles, boxes, plywood, tires, and trash cans—especially
if they are stored right next to the house. With attached garages, block off
house access by sealing cracks around doors and access holes for electrical
conduits or plumbing. In the Midwest, some brown recluse bites occur when a sleeping
person rolls over during the night, and the trapped spider bites in self
defense. In the bedroom, move the bed away from the wall, remove any skirts or
ruffles and remove all items stored under it. This minimizes chances that any
spider can crawl onto the bed. Do not leave clothes and shoes on the floor, or
shake them before dressing if they are left out. Apparel and equipment that is
only occasionally worn (gardening clothes and gloves, boots, baseball mitts,
roller skates, etc.) should be stored in tightly closed plastic bags,
especially if stored in the garage or other dark storage areas.
Typically, pesticide control of spiders is difficult
unless you actually see the spider and are able to spray it. There are various
insecticides available in retail outlets labeled for spider control. It is just
as easy and much less toxic for your living area to crush the spider with a
rolled up newspaper or your shoe. Sticky traps placed along floor boards out of
the reach of pets and young children offer a non-insecticidal way to trap
spiders as well as provide an idea of population levels in the structure. You
can also remove a spider from your home by placing a jar over it and slipping a
piece of paper under the jar that then seals off the opening of the jar when it
is lifted up. If you plan to send the spider to an expert for identification,
try to keep it in an undamaged condition because a crushed specimen may be
difficult to identify. If you can, soak the spider in rubbing alcohol for a few
days to preserve it first. You can freeze the spider first to facilitate safe
transfer into alcohol. If you send the spider in for
identification, do not mail alcohol as this is a violation of postal
regulations unless done exactly to the specifications for mailing flammable
fluids.
The Brown
Recluse, Violin or Fiddleback Spider.
Image courtesy of Joseph Berger. Bugwood.
The brown
recluse is a small-to-medium sized spider that is yellow to brown in color with
a distinctive violin shape marking on the cephalothorax. These spiders
have 6 eyes unlike most spiders that have 8.
The web is medium sized, irregular in shape with thick strands and is
not typically used to trap insects but rather more as a retreat. The recluse spiders prefer to live in close
spaces like between boxes, hanging or folded clothes, etc.
Both the males and females are dangerous. The venom
causes a local, necrotic reaction. The victim may not feel any pain for 2
or 3 hours after the bite or a painful reaction may occur immediately. In this case a stinging sensation is usually
followed by intense pain. A blister forms as well as a painful, reddish
margin. The victim has chills and a generalized rash. The tissue at
the center of the bite becomes necrotic and involves the skin as well as subcutaneous
tissue. In some cases the necrosis continues to increase resulting in a
huge open sore that can reach several inches in diameter. The healing is very
slow (up to several months) and often leaves an extensive scar. There is no
antivenin available, but the bite is often treated with corticosteroids and
excision of the bite area. In advanced cases the lesion may become so
large that amputation of limbs may be necessary.
Symptoms of Brown Recluse Spider a
Few Days after Bite. Image Courtesy of
Center for Disease Control.
Scar left from brown recluse bite. Image
Courtesy of Center for Disease Control.
Chilean Recluse Spider-Loxosceles laeta. In Spanish, it (and other South American recluse spiders) is known
as arańa de rincón, or "spider of the corner"; in Portuguese, as Aranha-marrom or "brown spider". This spider is considered by many
to be the most dangerous of the recluse
spiders, and its bite is known to
frequently result in severe systemic reactions, including death.
The Chilean
recluse is one of the larger species of recluse spiders, up to 1/12 inches in
length (including legs). Like most recluses, it is brown and usually has
markings on the dorsal side of its thorax, with a
black line coming from it that looks like a violin with the neck of the violin pointing
to the rear of the spider resulting in the nickname "fiddleback
spider" or "violin spider". Coloring varies from light tan to
brown and the violin marking may not be visible. Since the "violin
pattern" is not diagnostic, it is far more important, for purposes of identification,
to examine the eyes, as with its close relatives.
Chilean Recluse Spider.
The Chilean recluse spider
is native to much of South
America and can now
be found worldwide, including in North and Central
America, Finland, and Australia. The spider
is known to have established itself in the Los Angeles area, and infestations have been
reported in Vancouver,
British Columbia, Cambridge,
Massachusetts, and Florida. The
most recent reports indicate that this species no longer occurs in Los Angeles.
Like other
recluse spiders, the Chilean recluse builds irregular webs that frequently
include a shelter consisting of disorderly threads. Unlike most web weavers,
they leave these webs at night to hunt. People get bitten when they
unintentionally squeeze them in clothing and bedding. These spiders frequently
build their webs in woodpiles and sheds, closets, garages, and other places
that are dry and generally undisturbed. The spider frequently is found in human
dwellings. The spiders can last a long time without food or water, a fact that encourages their worldwide
spread.
As indicated
by its name, this spider is not aggressive and usually bites only when pressed
against human skin, such as when putting on an article of clothing. Like all Sicariidae spiders, the venom of the Chilean
recluse contains the dermonecrotic agent, sphingomyelinase D, which is
otherwise found only in a few pathogenic bacteria. According to one study, the
venom of the Chilean recluse (along with the six-eyed
sand spider), contains an order of magnitude more of this
substance than that of other Sicariidae spiders such as the brown
recluse.
Some bites
are minor with no necrosis, but a small
number produce severe skin necrosis or even systemic conditions (viscerocutaneous
loxoscelism); sometimes resulting in renal
failure and in 3-4%
of cases in a clinical study in Chile, death. The
serious bites form a running ulcer that
destroys soft tissue and may take months, and very rarely, years to heal,
leaving deep scars. The damaged
tissue will become gangrenous and eventually slough away. Initially
there may be no pain from a bite, but over time the wound may grow to as large
as 10 inches in extreme cases. Bites may take up to seven hours to cause
visible damage; more serious systemic effects may occur before this time, as
venom of any kind spreads throughout the body in minutes.
First aid
involves the application of an ice pack to control inflammation, the
application of aloe vera to soothe and help control the pain, and prompt
medical care. If it can be captured, the spider should be brought with the
patient in a clear, tightly closed container for identification. However, by
the time the bite is noticed any spider found nearby is not likely to be the
culprit. Unfortunately, 50% of children
bitten in South America die without treatment. Antivenin is available in
South America. The bite’s progress is slightly different from the recluse in
that the ulcerated area is dark rather than white. This spider is a
hunting spider that searches for prey away from its web and is nocturnal.
Desert Recluse Spider-Loxoceles deserta. This is
another relative of the more notorious brown recluse or violin spider. The distribution of this species in
California is quite limited occurring in isolated desert areas above 3,000 feet
elevation. This is a medium-sized,
non-descript tan species with many fine hairs covering the body. Very few people are bitten by this species
and the symptoms are similar, but far less severe, than that of the South
American violin or brown recluse spiders.
Very little
is known about the bite or symptoms of the other recluse spiders that are found
in the United States. The distribution of
these as is follows:
The Tucson
recluse, Loxoceles Sabina. Limited to Tucson area.
The Arizona recluse, Loxoceles arizonica. Central
and southern Arizona and SE California.
The Baja recluse, Loxoceles palma. Baja and
S.California.
The Big Bend recluse, Loxoceles blanchi. Western
Texas.
The Grand Canyon recluse, Loxoceles kaiba. Grand
Canyon.
Matha’s recluse, Loxoceles martha.
The Mediterranean recluse, Loxoceles rufescens. Introduced
species, several US cities. Bite not considered as toxic as some of the other
species.
Russell’s recluse, Loxoceles
russelli. Death Valley.
The Texas recluse, Loxoceles
devia. Texas.
The Tucson recluse, Loxoceles sabina. Tucson area.
Hobo Spider
The hobo spider (Tegenaria
agrestis) is a member of the genus of spiders known as funnel web spiders. It is
one of a small number of spiders in North America whose bites are generally
considered to be medically
significant. Individuals construct a funnel-shaped
structure of silk sheeting and lie in wait at the small end of the funnel for
prey insects to blunder onto their webs. Hobo spiders sometimes build their
webs in or around human habitations. Although this species of spider has a
reputation for aggressiveness even though they will normally avoid contact with
humans. Most bites occur when the spider is accidentally crushed or squeezed by
a human. The spider's venom is strong enough to cause considerable local pain
and possibly necrosis.
The toxicity
and aggression of the hobo spider are currently disputed by arachnologists. Its
nickname "aggressive house spider" comes from a misinterpretation of
the Latin name agrestis, which literally
translates to "of the fields", but has been mistranslated as "aggressive".
If a hobo spider is tending an egg sac, it may become aggressive if it
perceives the egg sac as being threatened. However, they generally do not bite unless
forced to protect themselves, and in the majority of cases the hobo spider does
not actually inject venom when it does bite.
In the United
States, the hobo spider has been considered to be a dangerous species based on
a toxicology study on rabbits where lesions appeared after spiders were induced
to bite the rabbits, although
attempts to replicate the study (by injecting venom to ensure envenomization)
have failed to produce necrotic
lesions, and there is even question as to whether the
lesions observed in the original study were necrotic. This laboratory study has led to the
proposal that in some parts of the U.S. nearly all bites imputed to the brown
recluse spider are in
reality the hobo spider's bite. The CDC and other U.S. government agencies
have also used this same study as the basis for a report claiming that the hobo
spider bite causes necrosis in humans despite the absence of any confirmed
cases. In Canada, there are scientists who claim that no hobo spider bites lead
to dermal necrosis. Hobo
spiders are common in Europe, though bites are relatively unknown, and there
are no confirmed reports of them causing necrosis despite hundreds of years of
coexistence there. The only documented case of a verified hobo spider bite
leading to necrotic skin lesions involves a person who had a pre-existing medical
condition (phlebitis) that can
also cause the appearance of skin lesions.
Hobo spider
bites are not known to be fatal to healthy humans. The necrosis in purported
cases is similar to, but milder than, that caused by the brown
recluse spider, and in severe cases can take months
to heal. Other reported symptoms include intense headaches, vision abnormalities,
and/or general feelings of malaise. These
symptoms are not confirmed for the hobo spider bite specifically due to lack of
positive identification of the spider by an expert, and the Oregon
Poison Center (affiliated
with the Oregon
Health & Science University) is attempting to gather
definitive evidence regarding the validity of these reports as of September
2007.
Hobo Spider.
Yellow Sac Spider
In females, the body measures between
5 and 9mm and in males, 4 to 8mm. The leg span however can be up to 1 inch
with the front pair of legs being longer than the other 3 pairs. Males tend to have a skinnier body and
a larger leg span than females. C.
inclusum gets its 2 common
names (yellow sac and black-footed spider) from its appearance. It is a pale
yellow-beige color with dark brown markings on its palps, chelicerae (jaws) and
on the ends of its tarsi (feet). There is also often an orange-brown stripe
running down the top-centre of its abdomen. In terms of sensory structures, C. inclusum has 8 similarly sized eyes distributed
in 2 parallel horizontal rows. However their eyes are thought to be less
important structures due to the absence of light during the spider's nocturnal
activity. The spider relies more on palps, sensory structures just behind the
chelicerae on the cephalothorax, to sense its environment.
Females of C. inclusum mate only once, and produce their
first egg mass about 14 days after mating. Two sets of eggs are usually
produced, but this can range anywhere from 1 to 5. Egg masses generally contain
17 to 85 eggs, although as many as 112 eggs have been reported in a single egg
mass. Egg lying
generally occurs during the months of June and July; during this period,
females lay their eggs in small (2 cm) silk tubes and enclose themselves
with the eggs, protecting them from predators. Females stay with the eggs and
juvenile spiders for about 17 days - until their first complete molt. Females
that produce multiple egg masses build a second egg sac about two weeks after
the juvenile spiders disperse. Males tend to mature faster (119 days on
average) than females (134 days on average), but time to maturity can range
from 65 to 273 days depending on a number of factors, such as temperature,
humidity and photoperiod. They over-winter mostly as adults or sub-adults.
Being nocturnal, this
spider feeds and mates at night. C. inclusum do not make webs to catch prey;
instead, they are active predators, feeding on a variety of arthropods such as
insects and other spiders. Prey detection may involve detection of mechanical
vibrations of the substrate, and vision seems to play an insignificant role. During the day, they retreat in
small silk nests similar to those used for reproduction. A new nest, which may
be completely closed, open on one side, or open on both sides, is built every
day in under 10 minutes. C. inclusum are known to disperse easily between trees
and shrubs. They do this by excreting a long silk thread that gets carried by
the wind and sticks to a nearby structure, forming a scaffold between two
structures. Alternatively, the spider may stay attached to the thread and become
airborne as the wind carries the thread in the air.
The bite of these spiders is believed
to be venomous to humans but rarely produces more
than local symptoms. They are believed to produce a high percentage of the
spider bites suffered by people, possibly because they wander about when people
cannot see well or are asleep, and so they may get squeezed and bite to protect
themselves. Bites that occur to farm laborers may occur because spiders hiding
in their shelters on leaves may get squeezed.
It has been
noted that a large number of bites attributed to the brown
recluse spider may actually
be the result of yellow sac spider bites, which possess a cytotoxic venom known to contain several
proteolytic enzymes including alkaline phosphatase, deoxyribonuclease, esterase, hyaluronidase, lipase, and ribonuclease. These enzymes
can cause localized tissue necrosis (which may be similar to that caused by a
recluse bite), though the symptoms are less severe and do not result in the
systemic effects occasionally seen with recluse envenomations.
However, the
view that this spider is dangerous to humans has been questioned. A recent
study of 20 confirmed yellow sac spider bites revealed no evidence of necrosis;
further review of international literature on confirmed bites revealed only a
single bite with mild necrotic symptoms.
Although the
danger of C. inclusum may be questionable, the spider bite
may cause local redness with stinging pain. When
it's found immediately wash from the bite site to prevent further venom
entering the wound in case of the spider bite. Thoroughly wash the wound with
soap and water. Do not use alcohol. Also do not engage in any activity that
raises the heart rate. An ice pack may be applied to draw out the venom. Do not
squeeze or pick the bite site. It may cause secondary infection or spread the
poison to a wider tissue region. If the pain persists for a long period, show
it to a doctor for a proper measure.
C. inclusum bites usually occur when the spider is threatened. People might threat C. inclusum without noticing in some incidents. For example, while C. inclusum is hunting during the night time, people may roll over and press the
spider accidentally or put on a coat that stayed in the closet over the winter
without noticing the spider inside.[13] Also, putting the shoes on while C. inclusum is in there. As the weather cools down, it is more likely for the spider
to invade the indoor structures. To prevent the bite from C. inclusum, secure all the screens on the windows and doors. Do not stack up the
fire woods near the house. Also, take care of all the house pests such as ants
and silverfish that attract spiders.
An adult yellow
sac spider. Image courtesy of Joseph Berger, Bugwood.
Tarantulas
Tarantulas
have received a “bad rap” from the moving picture industry for years. Actually in most cases the bite of a
tarantula is relatively harmless to humans.
That is to say the venom has little more effect than that of a bee
sting. Of course, as tarantulas are so
large, it follows that their chelicerae are large. In some of the large species of the world
these structures can reach one inch in length. In this case the bite will
result in a deep puncture wound and should be treated with a tetanus shot. As with many species of spiders little is
known about the toxicity of the venom of many tarantula species. This knowledge is becoming increasingly
important because of the recent interest in keeping tarantulas as pets. There are many tarantula breeders in the
United States and Europe. These
individuals conservatively breed over 100 species of tarantulas for the pet and
spider enthusiast trade.
Besides biting, New World tarantulas frequently
protect themselves by kicking off puffs of branched body hairs from the back of
their abdomens with their hind legs. The mucous membrane of the eyes and nose
of mammals, including humans, are quite sensitive to these hairs and resultant
watery eyes and severe itching of the skin may last for several hours. These
hairs can penetrate the skin up to 1/16 inch and frequently have a toxin
associated with them. People who handle tarantulas may develop an allergic
reaction to this venom, causing increased sensitivity and irritation after
minimal contact. Because the venom in the hairs is likely to be the same as
that in the fangs, someone who has developed sensitivity to the hairs could
have a more severe reaction upon being bitten.
The hairs are regenerated each time the tarantula molts.
Nicely Marked
Species of Tarantula and Chelicera or Fangs of an Average Sized Tarantula.
A goliath
tarantula -with its legs spread. This is one of the largest species of
tarantula-
frequently
reaching the size of a dinner plate.
Most tarantulas in the United
States feed on insects and, possibly young rodents. There are a number of
tropical species that live in trees (arboreal) and possibly feed on young birds
(the bird spiders). Many of the bird spiders are relatively slender bodied and
exceedingly hairy with long hairs extending at right angles from the body. The
authors were not sure of the function of these hairs until one day we
accidentally dropped a rather hairy one. While in midair, the spider extended
its legs in all directions and floated to the ground--much like a falling leaf.
The long hairs obviously increased the surface area of the spider, which along
with the spider's relatively light body, allowed it to perform this acrobatic
feat--a behavior that obviously has advantages when living in trees. The main diet of bird spiders is not birds
but insects.
The Mexican
Red-Knee. This is one of the most brightly colored and docile tarantulas known.
This species was collected by the thousands from Southern Mexico and imported
for years into the United States for the pet trade. Several years ago the
Mexican government prohibited this practice due to the depletion of the
species. Mexican red-kneed tarantulas occasionally can still be found in pet stores
but these come from tarantula breeders. They are typically available as tiny
spiderlings.
The
importation and exportation of animals and plants and/or their parts (e.g.,
Mexican red-knee, animal horns, and spotted cats) in many countries throughout the
world has become a major problem. As a result, a number of these countries have
formed an international agreement called the CITES Agreement. . Each country
has identified the plants and animals (including their parts) which they want
to protect. Once placed on a CITES list, an organism cannot be exported from a
country without a permit from that country. In many cases these permits are not
available. In the United States, the Fish and Wildlife Services enforces this
agreement. If they catch someone exporting or importing an illegal CITES
organism, the penalties can be quite severe. An individual recently was caught
bringing into the U.S about 80 Mexican red-knee tarantulas. He was sentenced to
6 years in jail.
In the news
today (August, 06) there was a case where an individual was caught trying to
import a number of illegal butterflies (CITES) including 2 Queen Alexander
birdwings-largest butterflies in the world-valued at $8500 each. He was indicted on 15 Federal charges as a
result of a three year investigation by the Federal Fish and Wild Life
Services. This individual was a fairly
well-known insect dealer.
A female red knee tarantula.
The authors were somewhat skeptical
about reports of a few incidences where a tarantula attempted to heal its own
wounds with its webbing. However, one day we were closing the cage door of a
Chilean rose-haired tarantula and accidentally chopped off part of its leg. As
blood began to ooze from the wound the tarantula spun several strands of silk
and wrapped it around the wound, thus effectively sealing it. Without this
tourniquet the tarantula would likely have bled to death. The Chilean rose-haired tarantula is the most
common species sold in pet stores. They
tend to be quite docile and in most cases are reluctant to bite.
A Chilean rose-haired tarantula-the
most common species available in pet stores.
The goliath spider from South
America is the largest species of spider in the world. A large specimen with
its legs fully spread will exceed the size of a dinner plate (10 inches). Some
of these giants of South America feed almost exclusively on lizards, frogs and
snakes. This spider is commonly referred to as a bird eater. This is a misnomer as these ground
inhabiting, heavy bodied spiders are rather slow moving and cannot climb all
characteristic which would be detrimental to catching birds. Apparently this name was probably acquired
because one of the original books published about spiders had a drawing of this
spider sitting next to a dead bird. When given a choice this tarantula prefers
the cold-blooded vertebrates to insects. Some of the more primitive human
tribes actively seek these giant tarantulas of the rainforest as a food source;
the spiders are roasted to remove the body hair. The eggs of a gravid female
are a special treat making a nice omelet! Tarantula is said to taste like
chicken; actually, it has a distinctive flavor of its own-I guess.
On one occasion we received a live adult
female goliath spider. As one of my colleagues and I were observing the spider,
I asked him, "Do you want to hold it?" He responded rather abruptly,
"No!" I replied, "Me
neither, let's feed it." It was a real monster, with at least one-inch
long curved fangs. So we proceeded to throw a large mouse in its cage. The
spider immediately jumped on the mouse and began pumping in salivary enzymes
with its needle shaped fangs. Upon our return the next day, there was nothing
left but a small ball of fur. The tarantula had consumed, everything else
including the bones. We never handled
that one-Ever.
A Goliath
spider-one of the largest tarantulas in the world.
All spiders
have fangs and poison glands (there are a few exceptions); however, many are
timid and will not or cannot penetrate the skin because their fangs are too
small. There is a tremendous lack of knowledge about the effect of the bite of
many common spiders in the world. A good
example of this is the brown recluse. As
mentioned above spider experts strongly feel that this spider no longer exists
in California. However, as with many
other hospitals, Redlands Community (a Southern California hospital) reports
treating several brown recluse bites a year.
If the spider experts are correct, there must other species of which we
are not aware, whose bite produces symptoms similar to that of the brown
recluse.
Jumping Spider-Family Salticidae. The jumping spiders are reportedly very
aggressive and on occasion bite humans.
The venom is not very potent and the bite is initially painful leaving 2
small red marks that heal in a few days.
Johnson’s jumping spider is the most common species that has been reported
to bite humans. This outdoor species is
nearly 1/2 inch long (big for a jumping spider) and has a black head with a
black and red body.
Two of many species of jumping spiders that
occasionally bite. Right image courtesy of Opoterser
This family contains
more than 500 described genera and about 5,000 described species, making it the largest family of spiders with about 13% of all species. They have good vision and use it for
hunting and navigating. They are capable of jumping from place to place,
secured by a silk tether.
Jumping spiders live in a variety of habitats with
tropical forests harboring the
most species, but they also commonly occurring in temperate forests, scrub
lands, deserts, intertidal
zones, and even mountains. Euophrys
omnisuperstes is a species
reported to have been collected at the highest elevation on the slopes of Mount
Everest.
They are generally diurnal, active
hunters. They possess a well-developed internal hydraulic system which
alters the pressure of body fluid within their legs thus allowing the spiders
to jump without large muscular legs. Some jumping spiders can jump 40 times
their body length. This is equivalent
to a 6 foot man jumping 240 feet.
When moving and especially just before it jumps, the spider tethers a
filament of silk to any available surface. Should it fall, it can then climbs
back up the silk tether. These spiders
are capable of jumping over 40 times their length.
Jumping spiders are known for their supposed curiosity. For example if
approached by a human hand, instead of retreating to safety as most spiders
would, the jumping spider will usually leap and turn to face the hand. Further
approach may result in the spider jumping backwards while still eyeing the
hand. The tiny creature will even raise its forelimbs and hold its ground.
Because of this contrast to other arachnids, the jumping spider is regarded as inquisitive as it is seemingly interested in
whatever approaches it.
An additional
distinctive characteristic is their large eyes.
These spiders have the best-developed visual system of all spiders,
which is used to best advantage when hunting prey. As do most spiders, they
have 4 pairs of eyes. One large pair and 1 small pair are oriented in a forward
facing position. Above this front row is
a second row of 2 tiny eyes and behind these there is a set of 2 large eyes
oriented in an upward position. As a result these spiders can see in a
360-degree plane. Unlike other spiders
they can move their eyes outward or inwards for focusing and they can be turned
up and down and from left and right. The spider can also turn its carapace
(breast) more than 45 degrees to look around. Jumping
spiders have very good vision centered in their anterior median eyes. Their eyes are able to create a focused image
on the retina, which has up to four layers of receptor cells. Physiological
experiments indicate that they have up to four different kinds of receptor
cells, with different absorption
spectra, giving them the possibility
of up to tetrachromatic color vision, with sensitivity extending into the ultraviolet range. All salticids are highly sensitive to UV light. The principal eyes have high resolution, but the
field of vision is narrow, from 2 to 5 degrees.
Eye Arrangement of a Jumping Spider. Image Courtesy of Noodle Snacks.
Jumping spiders are active hunters stalking their prey.
They use their superior eyesight to distinguish and track their intended meals,
often for several inches. Then, they pounce, giving the insect little to no
time to react before succumbing to the spider's venom.
Jumping Spider
with Heavily Fringed Palps for Mating Display. Image Courtesy of Peter Chew.
Mating recognition depends on visual courtship displays.
Males are often quite different in
appearance than females
and may have plumose hairs, colored or iridescent hairs, front leg fringes,
structures on other legs, and other, often bizarre, modifications. These are
used in visual courtship in which the colored or iridescent parts of the body
are displayed via vibrations, or zigzag movements for courtship
"dance". If the female is receptive to the male she will assume a
passive, crouching position. In some species, the female may also vibrate her palps or abdomen. The male will then extend
his front legs towards the female to touch her. If the female remains
receptive, the male will climb on the female's back and inseminate her with his
palps. In recent years it has been discovered that many jumping spiders may
have auditory signals as well, with amplified sounds produced by the males
sounding like buzzes or drum rolls.
Trapdoor
Spiders. Family Ctenizidae. Trapdoor
spiders are mygalomorph spiders that construct burrows with a
cork-like trapdoor made of soil, vegetation and silk. These relatively large spiders (adults reaching 1 to 1.5 inches in length)
are rarely seen as they spend the majority of their lives in well-designed
tunnels in the ground. The only time
that a trap door spider is commonly seen is when the male reaches sexual
maturity and strikes out in search of a female.
Otherwise they remain, grow and molt inside their tunnels. The entrance of the tunnel is typically
covered by an earthen door that is hinged at one end. The door is extremely difficult to spot as it
blends in with the surrounding environment.
A Trap Door
Spider.
Trap door
spiders do not leave their burrows to hunt but merely wait with the door
partially open for passing prey. Their
eyesight is not well developed and they rely on sensitive hairs on their legs
to pick up the vibrations of a passing prey.
Some species actually place elongated twig or silken strands radiating
out from the entrance to increase the distance of detection from the entrance.
Door of a Trap Door Spider with Silken
Stands Radiating Outward to Detect Potential Prey.
The burrow
and door serve not only as a home and means to capture prey, but also protects
the spiders from rain, regulates the humidity and temperature, and helps
protect them from potential predators, such as centipedes, scorpions and
parasitic wasps. In some species the spider has a set of spines on its legs,
which it presses into the side of the burrow while it holds the door shut with
its fangs. We once tried to pry open the
door of one of these spiders with a spoon and actually bent the handle in doing
so. It is now known that this spider can withstand the pull of 38 times its
weight.
A hungry
individual will wait halfway outside of its burrow for a meal. Male trapdoor
spiders can overcome the female's aggressive reactions to their approach, but
it is not known how. Females never travel far from their burrows, especially if
they have an egg sac. During this time, the female will capture food and
regurgitate it to feed her spiderlings. Enemies of the trapdoor spider include
certain pompilids (spider wasps), which seek out the burrows and manage to
gain entrance. They sting the owner and lay their eggs (usually one per spider)
on its body. When the egg hatches, the larva devours the spider alive.
Unlike other mygalomorph spiders, the Ctenizidae have a rastellum on the chelicera. This structure
resembling "teeth" or "barbs" on each fang is used to dig
and gather soil while constructing a burrow.
Some species
store the remains of their prey and other debris behind the silk lining of the
tunnel. If a potential predator breaks
into the tunnel, the spider will rush to the bottom of the tunnel while
simultaneously releasing the debris and silk lining, thus forming a false
bottom to the tunnel and concealing the spider beneath.
Hollywood Trapdoor Species. Aptostichus stephencolberti is a species of trapdoor
spider named after the American satirist Stephen
Colbert. The spider was discovered on the California coastline in 2007. This species is found on coastal dunes that extend
from the Big Sur area to the San
Francisco peninsula at Point Lobos and Golden Gate. Compared to closely-related species
such as Aptostichus
angelinajolieae (named after Angelina
Jolie), Aptostichus
stephencolberti is lighter in color. The male
holotype and the female paratype both have brownish yellow legs, carapace and chelicerae, while the abdomen is lighter with dusky stripes. The
male has six teeth, while the female has five.
The spider was named after Colbert after he reported on his television
series The
Colbert Report that Jason Bond, a professor
of biology at East Carolina
University, named a different species of spider Myrmekiaphila
neilyoungi, after the Canadian rock star Neil Young. Colbert was
angered by the fact that Bond had not named a spider after him, and began to
appeal for a species of animal to be named after him. He claimed that he
already had an eagle and a turtle named after him, so there was no reason that
another animal could not be named after him as well.
On a later edition of The
Colbert Report, Colbert revealed that Bond would name a spider after him,
with Colbert claiming, "And all I had to do was shamelessly beg on
national television." The
two men talked on the telephone to decide which spider should be the one to be
so named, but as there were 27 different species of spider available, Bond was
left to make the final choice.
The name Aptostichus
stephencolberti was
officially announced as the spider named after Colbert on The Colbert Report on August 6, 2008. Because Colbert pronounces his surname
with a silent "T", the last "T" in stephencolberti is also silent.
Grass Spider. This is
another species of common spider that reportedly bites humans. This species is a little less than ˝-inch in
length with 2 dark parallel stripes running the length of the cephalothorax. The overall body color is tan with modeled
white markings. This spider inhabits
gardens and junk piles and lives under stones and logs. The web is trampoline-like in shape and
tapers back into a funnel where the spider hides and waits for its prey. This species can produce a painful bite due
to its powerful jaw muscles and large fangs.
The nature of the venom is unknown.
Typically a bite will cause mild swelling and a red spot. There have been some recorded cases of more
severe symptoms. This could possibly be
due to allergic reactions to the venom.
A grass spider
frequently bites resulting in mild swelling.
Orb-Weaver
Spiders. Family Araneidae. Characterized by
spiral wheel-shaped webs they are often found in gardens, fields and forests.
Their common name is taken from the round shape of this typical web.
Orb-weavers have eight similar eyes, legs hairy or spiny and no stridulating organs. The family is cosmopolitan, including many
well-known large or brightly colored garden spiders. There are more than 2,800 species in over 160 genera worldwide, making this the third largest family of spiders known behind Salticidae and Linyphiidae.
Generally, orb-weaving spiders are three-clawed builders
of flat webs with sticky spiral capture silk. The
building of a web is an engineering feat, begun when the spider floats a line
on the wind to another surface. The spider secures the line and then drops
another line from the center, making a "Y". The rest of the
scaffolding follows with many radii of non-sticky silk being constructed before
a final spiral of sticky capture silk. The third claw is used to walk on the
non-sticky part of the web. Characteristically, the prey insect that blunders into the sticky lines
is stunned by a quick bite and then wrapped in silk. If the prey is a venomous insect, such as a wasp, wrapping may
precede biting.
Many
orb-weavers build a new web each day. Generally, towards evening, the spider
will consume the old web, rest for approximately an hour, and then spin a new
web in the same general location. Thus, the webs of orb-weavers are generally
free of the accumulation of detritus common to other species such as black widow spiders.
Some
orb-weavers do not build webs at all with these include members of the genera Mastophora in the Americas, Cladomelea in Africa and Ordgarius in Australia. This group of spiders has a rather unique means of catching their prey.
They are part of a tribe of the orb-weaving spider family (Araneidae) that no
longer build an orb web, but instead attract their prey (male moths) by
chemical mimicry. The moths are captured using a "bolas" which is a
sticky ball of glue attached to a strand of silk. The spider swings this around
until the ball hits and sticks to the approaching moth. The moth is then reeled
in by the spider and then webbed up in silk.
This would be a pretty inefficient means of capturing prey if done at
random. The chance of catching a moth
that merely flew by would be pretty remote.
However, the spider actually emits a sex pheromone that mimics that
produced by female moths to attract males for mating. Instead of finding a mate the males end up as
dinner for the bolas spider. Even more
amazing this spider feeds on 2 different species of moths each of which fly and
typically mate at different times of the night-one early in the evening and
another late at night. Accordingly the
bolas spider produces and releases 2 different pheromones each at the correct
time that correspond to when each species flies.
An Australian female bolas spider and an American
bolas spider swinging its sticky ball.
Images courtesy of Dave Britton.
An equally
amazing feature of this spider is the huge size of their egg sacs. Typically
several of these giant are produced by the female. It is thought that she is capable of doing
this due to the small amount of silk used in catching her prey.
A Female Bolas Spider Sitting on One of its Several Egg Masses. Image
Courtesy of Dave Britton.
The spiny
orb-weaving spiders in the genera Gasteracantha and Micrathena look like plant seeds or thorns
hanging in their orb-webs. Some species of Gasteracantha
have very long horn-like spines protruding from their abdomens.
One feature of the webs of some orb-weavers is the stabilimentum, a
crisscross band of silk through the center of the web. It is found in a number
of genera, but Argiope, which
includes the common garden spider of Europe as well as the yellow and banded
garden spiders of North America, is a prime example. The band has been
hypothesized to be a lure for prey, a marker to warn birds away from the web
and a camouflage for the spider when it sits in the
center of the web. However, recent research suggests that the stabilimentum
actually decreases the visibility of the silk to insects, thus making it harder
for prey to avoid the web.
Orb web with stabilimentum. Images courtesy Peter Chew, Brisbane Insects.
Golden Web
Spiders. Anyone who has been in the tropics (east and west) has undoubtedly come
across the golden web spiders in the genus Nephila. These are beautiful
monsters. The adult females of some
species can reach a body length of two with a leg span of eight inches. They are quite beautiful with many iridescent
colors. In comparison to the females,
the males are minute, in some species 1,000 times smaller than the female. The males are normally found in the same web
as the female, but are not in danger of being eaten because they are so small
that the female does not recognize them as food.
Typical (Costa Rican) golden orb web spiders. The web of this spider is so strong that it
can trap birds and bats. Note small male
in right image (top-middle).
As amazing as
are these spider, their web is even more impressive. The silk itself is a golden color and quite
strong. The silk is so strong that
birds, bats and lizards are frequently trapped and consumed. The webs
themselves are large, with the central hub of the web reaching six to seven
feet in diameter width and the radiating supporting strands attach as much as
20 feet apart. The webs are so extensive
that these spiders typically do not make new webs but continuously repair the
old one. The webbing of these spiders is
so strong that the natives in some of the Pacific island use it for fishing
line.
As impressive
as these spiders are they are not impervious to competition or even predation
from other spiders. On one of our
student trips to Thailand I was walking along a trail in the mountains and came
across a large female Nephila spider
that had recently caught and was feeding on a small bird. I noticed that there were 2 other spiders
(about 1/20th her size) feeding on the same bird. Apparently there are a number of other
spiders that “pirate” feed on the prey of this species. Argyrodes,
a close relative of the black widow, is one of the main spiders that
exhibit this behavior. This spider
typically builds its web close to that of the golden web spiders but makes
frequent excursions onto the web of the giant.
Once this pirate determines that Nephila
has made a catch it waits until the prey is subdued, tightly wrapped with the
giants silk and moved to a storage location on the web. At that point Argyrodes carefully moves toward the prey avoiding vibrating her web so not to end up
as desert. Once locating the prey Argyrodes cuts the filaments that
support the wrapped package and steals away with its prize. The orb spider’s web is so large that it is
not uncommon for up to 40 of these pirates to feed off its catch. If pickings are slim these pirates on
occasion will attack, subdue and eat the orb spider.
Most arachnid webs are vertical and the spiders usually hang with their
head downward. A few webs, such as those of orb-weaver in the genus Metepiera have the orb hidden within a tangled
space of web. Some Metepiera are semi-social and live in communal
webs. In Mexico such communal webs have been cut out of trees or bushes and
used for living fly paper.
The oldest known true orb-weaver is Mesozygiella dunlopi, from the Lower Cretaceous. Several
fossils provide direct evidence that the three major orb weaving families,
namely Araneidae, Tetragnathidae and Uloboridae, had evolved by this time,
about 140 million years ago. They probably originated during the Jurassic
(200-140 million years ago). All three families very likely have a common
origin.
Lynx
Spiders-Family Oxyopidae. Lynx Spiders are hunting spiders that spend their lives on plants,
flowers and shrubs. Nimble runners and jumpers, they rely on their keen
eyesight to stalk, chase or ambush prey. Six of their eight eyes are arranged
in a hexagon-like pattern, a characteristic that identifies them as members of
the family. They also have spiny legs. Common genera in the United States
include Oxyopes—the common lynx spiders—and Peucetia—the green lynx spiders.
Some members
of the genus Oxyopes are abundant enough to be important in
agricultural systems as biological control agents. This is especially true of
the striped lynx spider (Oxyopes salticus). A member
of the genus Tapinillus is remarkable as being one of the few social
spiders, living in colonies.
Lynx Spider in Genus Oxyopes-Important
in Biocontrol. Image Courtesy Kaldari-en
Wikipedia.
Peucetia
viridans, the green lynx spider, is a conspicuous bright-green
spider found on shrubs. It is the largest North American lynx spider. The species name, viridans, is Latin for "becoming
green".
The female reaches a body length approaching an inch in
length; the more slender male averages ˝ inch. There usually is a red patch
between the eyes, with red spots over the body. The eye region is clothed with
white flattened hairs. The legs are green to yellow, with very long black
spines, and covered with black spots. It is rather similar to other species to occur in the United
States. Gravid females are able to change their color to
fit their background; however, this takes about 16 days.
The green lynx
spider is capable of spitting its venom a few inches. Image courtesy of Russ Ottens, Univ. Georgia.
The female
constructs one to four egg sacs in September and October, each containing 25 to
600 bright orange eggs, which she guards, usually hanging upside down from a
sac and attacking everything that comes near. The eggs hatch after about two
weeks, and after another two weeks fully functional spiderlings emerge. They
pass through eight instars to reach maturity. this non venomous
spider is usually found on foliage.
The green lynx spider very
seldom bites humans, and its bite is harmless though painful. It
is a common predator in cotton and other crops. This species is found in gardens, chaparral, on flower heads of wild
buckwheat, in tall grass and bushes where it hunts and captures its prey
without the use of a web. The green lynx
is capable of biting and spitting its venom a distance of a few inches. If it reaches the eyes the venom may cause
irritation that will clear up in a few days. The spiders have been
observed to hunt several moths species and
their larvae, including some of the most important crop pests, such as the
bollworm moth (Heliothis zea), the cotton
leafworm moth (Alabama
agrillacea) and the cabbage looper moth (Trichoplusia ni). However,
they also prey on beneficial insects, such as honey bees.
Wolf Spiders-Lycosidae. The family name Lycosidae, from the Greek word
"λύκος" means "wolf". They are
robust and agile hunters with good eyesight but unlike wolves but live mostly
solitary lives and hunt alone. Some are opportunistic wandering hunters,
pouncing upon prey as they find it or chasing it over short distances. Others
lie in wait for passing prey, often from or near the mouth of a burrow.
Wolf spiders
resemble nursery web
spiders (family Pisauridae), but they carry
their egg sacs by attaching them to their spinnerets (Pisauridae carry their egg sacs with
their chelicerae and pedipalps). Wolf
spiders have two eyes out of eight that are large and prominent. The eight eyes
of the Nursery web spiders are all of approximately equal size.
There are
many genera of wolf spider, ranging in body size from less than 1 to 0.04 to
1.18 inch. They have eight
eyes arranged in three rows. The bottom row consists of four small eyes, the
middle row has two very large eyes, and the top row has two medium-sized eyes.
They depend on their eyesight, which is quite good, to hunt. Their sense of
touch is also acute.
Eye
Configuration of Wolf Spider. Image Courtesy Opoterser.
Wolf spiders are unique in carrying their egg sac, which they attach to
the spinnerets at the end of their abdomen. The abdomen is held in a raised
position to keep the egg case from dragging on the ground, but they are still
capable of hunting while so encumbered.
Female Wolf
Spider with Attached Egg Sac. Image
Courtesy of Fir0002 at en.wikipedia
Also unique
to wolf spiders is their method of infant care. Immediately after the little
spiders hatch and emerge from their protective silken case, they clamber up
their mother's legs and all crowd onto her abdomen.
Female Wolf Spider Carrying Spiderlings. Image Courtesy
Wikipedia Commons.
Their eyes
readily reflect light. One method of finding them is to hunt at night using a
flashlight strapped on the forehead so
that the light is reflected
from their eyes directly back
toward its source. Because they depend
on camouflage for protection, they do not have the flashy appearance of some
other kinds of spiders. In general their coloration is appropriate to their
favorite habitat.
Hogna is the genus with the largest of the wolf spiders. Among the Hogna species in the U.S., the nearly solid
dark brown H. carolinensis is the largest, with a body that can
be more than one inch long. It is sometimes confused with H. helluo (pictured below), which is somewhat
smaller and entirely different in coloration.
Some members of the Lycosidae, such as the Carolina
wolf spider make deep tubular burrows in and around which they lurk much of the
time. Others, such as H.
helluo, seek shelter under convenient rocks and other such shelters as
nature may provide. They may wander from place to place, and are therefore more
likely to be the ones attracted into human habitation when the weather starts
to turn colder in autumn.
There are many smaller wolf spiders.
They patrol pastures and fields and are an important natural control on harmful
insects. Wolf spiders are capable of defensive bites, and some South American
species may give bites that are medically significant. Wolf spiders will inject venom freely if continually provoked.
Symptoms of their bite include swelling, mild pain and itching. Though usually
considered harmless to humans, the bite of some species can be painful. In the
past, necrotic bites have been attributed to some South
American species, but further investigation has indicated
that those problems that did occur were probably actually due to bites by
members of other genera. Australian wolf spiders have also been associated
with necrotic wounds, but careful study has
likewise shown them not to produce such results.
Wolf spiders
can be found in a wide range of habitats both coastal and inland. These include
shrublands, woodlands, wet coastal forest, alpine meadows, and suburban
gardens. Spiderlings disperse aerially (ballooning) and consequently wolf
spiders have wide distributions. Although some species have very specific microhabitat needs most are wanderers without
permanent homes. Some build burrows which can be opened or have a
trapdoor. Arid zone species construct turrets or plug their holes with leaves
and pebbles during the rainy season to protect themselves from flood waters.
Araneomorph Funnel-Web
Spiders-Agelenidae.
Other common names of these
spiders include funnel weavers, cobweb and grass spiders. Because many other
spiders are similar in appearance to them, these spiders are most easily
distinguished by the shape of their webs rather than the spiders themselves. They weave a tubular funnel, which is used as
a retreat and is located at one the silken sheet of the web. Any prey that lands on the sheet is caught
and consumed in the retreat. The egg sac is found in the funnel and the male
often stays with the female, which is rare in arthropods and becoming somewhat
rare in human marriages. As the second common name suggests, they can be found
in tall grass. These spiders
occasionally enter homes. This is
certainly not their normal habitat and typically results from the males
wandering and looking for a female and blundering into the structure. The human
female they find there is usually not so happy to see them.
A common funnel
web, cobweb or grass spider. Image
courtesy of Joseph Berger-Bugwood.
This family
includes the common grass spiders of the genus Agelenopsis, as well as
the purportedly venomous European hobo spider, Tegenaria agrestis, which has
been introduced into the Pacific Northwest of the United States. The araneomorph funnel-web spider should not to be confused with the funnel-web tarantula and the venomous funnel-web tarantula. The venomous funnel-web tarantulas include the infamous Sydney funnel-web spider.
There are nearly 500 species in over 40 genera
worldwide. Among other genera are Hololena
and Agelena. The last
named genus includes some fascinating semi-social spiders that live in complex
communal webs in Africa. The best known of these is probably Agelena consociata.
Sociality in these spiders has gone so far as communal web-building and sharing;
cooperative prey capture and communal rearing of young. Spiders have not,
however, taken the final step into the social behavior of the social Hymenoptera (ants, bees and wasps) because there are no workers or soldiers (no
castes) and all females are reproductive.
Most of these
spiders are also known for their fast speed which, on the web, can reach 2 km/h
(slow-paced pedestrian walk). Due to this ability, they practically rely solely
on their movement while capturing prey, but, unlike similar families, Lycosidae for example, they prefer to stalk
their prey by building randomly placed web sheets, which may include up to 100
times the spider's size and funnel down to a narrow nest, hence the spider's
name.
Funnel Web Spider in Web. Image
Courtesy of Pollinator en Wikipedia.
Usually,
Agelenids range from 1/4 to ˝ inch in size, excluding leg span, and about 2
inches in the largest species, including the legs.
Agelenids
have a disputable reputation of a bite that could be highly venomous to humans,
however, this has never been completely proven. Of all the genera, Tegenaria species
probably have the most potent venom, but cases of a medically considerable spider bites occurring from them are generally scarce.
DaddyLongleg
Spiders-Family Phlocidae. Some species are also commonly called granddaddy long-legs spider, daddy long-legger, cellar spider, vibrating spider, or house spider. Pholcids are fragile
spiders, the body being 1/10 to 4/10 in length with legs which may be up to 2
inches long. They have cylindrical abdomens and the eyes
are arranged in two lateral groups of three and two smaller median contiguous eyes. Eight and six eyes both occur
in this family. Other species have a small globose abdomen with eyes are arranged in two
groups of three and no median eyes. Pholcids are gray to brown with banding or
chevron markings.
Eye Pattern of
Daddy-Two Set of Three Closely Grouped Eyes. Image Courtesy Benpcc.
These spiders
have very long legs and look similar to the harvestmen or true daddy longlegs.
The harvestmen are not true spiders and actually belong to a separate order
(Phalangida), as discussed earlier. An easy way to distinguishing the two is
that the true daddy longleg has a segment abdomen while the spider does not.
The members of the daddy-longlegs spiders are the most common spiders that are
found in houses and buildings. My wife really like spiders and doesn’t want me
killing these spiders that inhabit our house.
Consequently we don’t have to decorate that much for Halloween. When it gets really bad I sometimes sneak out
with the vacuum at night. When disturbed or under threat of attack, they
violently vibrate their web in attempt to discourage the intruder, hence
another common name of the vibrating spiders.
Some indications are that this spider has very toxic venom; however,
their fangs are too small to penetrate the skin and are not considered
dangerous. (Pat’s note: Dick doesn’t know it, but I go back out and sneak them
back in after he goes to sleep.) (Dick’s
note. I do now!)
True Daddy Longlegs, Not to be confused with Daddy Longleg Spiders. Images Courtesy of Joseph Berger, Colorado State Univ., Bugwood.
These spiders
spin untidy webs that are readily abandoned if they become dirty. When webs are abandoned, the spiders
immediately spin new webbing, thus accounting for the large amount of webs that
can be found in a home with relatively few spiders. The main webbing is
relatively weak and typically is not used to trap prey and is primarily used
for retreat. Likewise their chelicerae
are also too small to hold prey. This
spider traps its prey by throwing tough, stiff web material over the victim.
After the prey is motionless, it is wrapped and subsequently pumped full of
digestive enzymes. These spiders are capable of subduing almost any type of
arthropod including larger wolf spiders, black widows and even other daddy
longlegs. Even though the average
homeowner is unwilling to put up with them, these spiders are quite effective
predators and can significantly reduce the presence of other bugs in the home.
In the winter
when the general insect population is at its lowest, the spider moves through
the house on hunting expeditions. On such occasions it even starts looking for
the web of other species of spiders. If found it will vibrate the web
(simulating a captured prey) in combination with acting like a captured
prey-this behavior includes twitching its abdomen, bouncing in place and
shivering and tensing while contracting its legs toward its body. All these behaviors tend to excite the other
spider which emerges expecting a capture prey but is consumed by the larger
long-legged cellar spider.
Daddy-longleg or
cellar spider.
This species
originally came from the tropics and in colder climates is found only inside
houses. Unlike most other spiders, daddy
longlegs breed throughout the year. The
fertilized eggs are not spun in a cocoon, but are held in a small net of silk.
Because the spider is always on the move, it is common to see a female carrying
her sac of 20 to 30 eggs with her.
Brazilian Wandering Spiders, Armed Spiders or Banana Spiders-Phoneutria spp. The last name should
not to be confused with the relatively harmless species of the genus Nephila. This a genus of aggressive and highly venomous spiders found in tropical South and Central
America. These spiders are members of
the Ctenidae family of wandering spiders. The genus Phoneutria (Greek for "Murderess")
contains eight species. The Brazilian wandering spiders can grow to have a leg
span of up to 4 to5 inches. Their body length ranges from
0.7–1.9 inches. The wandering
spiders are
so-called because they wander the jungle floor at night, rather than residing
in a lair or maintaining a web. During the day they hide inside termite mounds, under fallen logs and rocks, and in banana plants and bromeliads. P. nigriventer is known to hide in dark and moist
places in or near human dwellings.
Brazilain Wandering
Spider. Image Courtesy of Teuchser.
They have a
distinctive defensive display in which the body is lifted up into an erect
position, the first two pairs of legs are lifted high (revealing the
conspicuous black-striped pattern on their underside), while the entire animal
sways from side to side.[3]
They are found in forests from Costa Rica throughout South
America east of
the Andes into northern Argentina, including Colombia, Venezuela, the Guianas, Ecuador, Peru, Bolivia, Brazil and Paraguay. Two species (P. reidyi and P. boliviensis) are found from southern Central
America to the Amazon
region, while one species (P. fera) is restricted to the Amazon. The remaining species are
restricted to Atlantic
Forest of Argentina, Paraguay and
Brazil, including forest fragments in the Cerrado (savannah). In Brazil, Phoneutria is only absent in the northeastern region north of Salvador,
Bahia. Phoneutria has been introduced to Chile and Uruguay.
P.
nigriventer is the most venomous species of spider. Its venom contains a potent neurotoxin, known as PhTx3, which acts as a broad-spectrum calcium
channel blocker that inhibits glutamate release, calcium uptake and also glutamate uptake in neural
synapses. At deadly concentrations, this
neurotoxin causes loss of muscle control and breathing problems, resulting in
paralysis and eventual asphyxiation. In addition, the venom causes intense pain and inflammation following an attack due to an excitatory effect the venom has on the serotonin 5-HT4 receptors of sensory nerves. This sensory nerve stimulation causes
a release of neuropeptides such as substance P which triggers inflammation and pain.
Aside from
causing intense pain, the venom of the spider can also cause priapism (prolonged erection of the penis or clitoris-several
hours in some cases) in humans. Erections resulting from the bite are
uncomfortable, can last for many hours and can lead to impotence. A component
of the venom (Tx2-6) is being
studied for use in erectile
dysfunction treatments.
The amount of P.
nigriventer venom necessary
to kill a 20 g mouse has been shown to be only 6 μg intravenously and 134 μg subcutaneouslyas compared
to 110 μg and 200 μg respectively for Latrodectus mactans (Black Widow). Laboratory
mice subjected to P.
nigriventer venom experienced
intense penile erections before succumbing to the toxin. This ranks Phoneutria venom among the most deadly found in
spiders.
Phoneutria includes some of the relatively few
species of spiders known to present a threat to human beings. Danger to humans
is not merely a question of toxicity, but requires the capacity to deliver the
venom, a sufficient quantity of venom, a disposition that makes a bite likely
and proximity to human habitation. The actual incidence of death or serious
injury must also be considered.
Spider mouthparts evolved to inject venom into very small prey. They are not well-adapted to attacking large
mammals such as humans. Recent studies
suggest that Phoneutria inject venom in approximately
one-third of their bites, and only a small quantity in one-third of those
cases.
Of the eight described species, P. nigriventer and P. fera most frequently receive mention in
mass-media publications. P. nigriventer is the species responsible for most
cases of venom intoxication in Brazil because it is commonly found in highly
populated areas of south-eastern Brazil, such as the
states of Săo Paulo, Minas Gerais, Rio de
Janeiro and Espírito Santo. The species P. fera is native to the northern portion of
South America in the Amazon of Brazil, Venezuela, Ecuador, Peru and the Guyanas.
The spider's
wandering nature is another reason it is considered so dangerous. In densely
populated areas, Phoneutria species usually search for cover and
dark places to hide during daytime, leading it to hide within houses, clothes,
cars, boots, boxes and log piles, thus generating accidents when people disturb
its. Its other common name "banana spider" is attributed, because of
its tendency to hide in banana bunches on plantations, and is occasionally
found as a stowaway within shipments of bananas. These
spiders can also appear in banana crates sent to grocery stores and bulk food
centers around the world. One such instance happened with a shipment of bananas
arriving at Bridgwater, England, when a man was bitten by a P. fera; however, due to quick
medical care he survived, taking nearly a week to recover from the bite
following treatment.
Despite their
reputation as the world's deadliest spiders, there are multiple studies that
call in to question their capacity for fatal human envenomation, though some of
these are labeled with a level of uncertainty, as Phoneutrias easily can be confused with other
species such as the Lycosides or other large labidognatha spiders. One study suggested that
only 2.3 % of bites (mainly in children) were serious enough to require antivenom. However, other studies indicated that
the toxicity of Phoneutria venom was clearly more virulent than
both Latrodectus and Atrax. Many
experts believe that various spiders like Phoneutria can either deliver a "dry"
bite or purposely conserve their venom, as opposed to a more primitive spider
like Atrax that usually delivers a full load.
Nevertheless, there are well-attested instances of death. In one case, a single
spider killed two children in Săo
Sebastiăo. The spider was positively identified as a Phoneutria.
Australian Funnel-Web Spider. Family- Hexathelidae. This
family includes an estimated 40 species of Hadronyche and a sole species of the genus Atrax robustus, the notoriously
dangerous Sydney
funnel-web spider. These
spiders are medium-to-large in size, with body lengths ranging from 0.4"
to 2 inches. They are darkly colored, ranging from black to brown, with a
glossy carapace covering the front part of the body. They have long spinnerets; this is especially true of A. robustus.
Like other Mygalomorphae —an infraorder of spiders that includes the tropical tarantulas —these spiders have fangs which point straight down the body
and do not point towards each other. They have ample venom glands that lie entirely within their
chelicerae. Their fangs
are large and powerful, capable of penetrating fingernails and soft shoes.
Sydney Funnel-Web Spider
with Huge Fangs en:User:Tirin, www.takver.com
Funnel-webs make their burrows in moist, cool, sheltered habitats—under rocks,
in and under rotting logs, some in rough-barked trees (occasionally meters
above ground). They are commonly found in suburban rockeries and shrubberies,
rarely in lawns or other open terrain. A funnel-web's burrow characteristically
has irregular silk trip lines radiating from the entrance. Unlike some related trapdoor
spiders, funnel-webs do not build lids to their burrows.
The primary
range of the Australasian funnel-web spiders is the eastern coast of Australia, with
specimens found in New South
Wales, South
Australia, Victoria, and Queensland. In addition, some specimens have been
found in other islands in the south Pacific. The only Australian states without
funnel-webs are Western Australia and
the Northern Territory.
Funnel-webs
are one of the three most dangerous spiders in the world and are regarded by
some to be the most dangerous. Examination of bite records has implicated wandering
males in most if not all fatal funnel-web bites to humans. Adult males,
recognized by the modified terminal segment of the palp, will defend
themselves vigorously if they feel threatened and tend to wander during the
warmer months of the year looking for receptive females for mating. They are attracted to water and hence
are often found in swimming pools where they have fallen while wandering. The
spiders can survive such immersion for several hours and can deliver a bite
when removed from the water. They also show up in garages and yards in suburban Sydney. Contrary to
a commonly held belief, no funnel-web spider is able to jump, although they can
run quickly.
While some very venomous
spiders may give dry bites, these spiders do so much less frequently. An inefficient mode of delivery (to
large animals) and interrupted contact are also possible causes of low volume
delivery. It has been claimed that approximately 10% to 25% of bites will
produce significant toxicity but
the likelihood cannot be predicted and all should be treated as potentially
life-threatening.
There have been 26
recorded deaths in Australia in the last 100 years from spider bites. Bites
from Sydney
funnel-web spiders have caused
13 deaths (seven in children). In all cases where the sex of the biting spider
could be determined, it was found to be the male of the species. Most
victims were young, ill or infirm. One
member of the genus Hadronyche,
the northern
tree funnel-web has also been
claimed to cause fatal envenomation but,
to date, this lacks the support of a specific medical report. Assays of venom
from several Hadronyche species
have shown it to be similar to Atrax venom.
There are many different toxins in the venom of Atrax and Hadronyche spiders. Collectively, these spider
toxins are given the
name atracotoxins (ACTX). These toxins are thought to operate by opening sodium
channels. They are pre-synaptic neurotoxins that (via
sodium channels) induce spontaneous, repetitive firing of action
potentials in autonomic
and motor neurons and inhibit neurally mediated transmitted release resulting
in a surge of endogenousacetylcholine, noradrenaline and adrenaline.
Although extremely
toxic to primates, the venom appears to be fairly harmless to many other
animals. It has been suggested that these animals may be resistant to the
venom's effects due to the presence of IgG, and
possibly cross-linked IgG and IgM inactivating factors in their blood plasma that bind to the toxins responsible
and neutralize them, or it may involve a non-specific reaction due to the
highly basic nature of the toxins.
The female venom was thought to be only about a sixth
as potent to humans as that of the male but
recent research has proven that false. The bite of a female or juvenile may
be serious; however, considerable variability occurs in venom toxicity between
species, together with assumable degrees of inefficiency in the method of venom
delivery.
Envenoming
symptoms observed following bites by these spiders are very similar. The bite
is initially very painful, due to the acidity of the venom and the size of the
fangs penetrating the skin. Systemic envenoming may follow the local effects.
Early symptoms of systemic envenoming include tingling around the mouth and
tongue, facial muscle twitching, nausea, vomiting, profuse sweating,
salivation, and shortness of
breath. Patients may rapidly develop agitation, confusion and coma associated with hypertension, metabolic
acidosis, dilation of
the pupils, generalized muscle twitching and pulmonary
edema. Death
results from progressive hypotension or possibly raised intracranial
pressure consequent of
cerebral swelling.
The onset of severe envenoming can be rapid. In one
prospective study, the median time to onset of envenoming was 28 minutes, with
only two cases having onset after 2 hours (both had pressure immobilization
bandages applied). Death may
occur within a period ranging from 15 minutes (this
occurred when a small child was bitten) to three days.
First aid for funnel-web bites consists of applying a pressure
immobilization bandage.
Pressure immobilization is the wrapping of the bitten limb with a crepe bandage
and splint. It was originally developed for snake bites but has been shown to be effective at
slowing venom movement in funnel-web bites and may also slowly inactivate the
venom.
Further
supportive care may be necessary, but the mainstay of treatment is antivenom. Antivenom
is raised against male Atrax
robustus venom but appears to
be effective for all species of funnel web spiders. Funnel-web antivenom has also been
shown to reverse the in vitro effects of Eastern Mouse spider (Missulena bradleyi) venom.
Prior to the
introduction of antivenom, envenoming
resulted in significant morbidity and mortality. Fortunately, the antivenom is
fast-acting and highly and globally effective. Antivenom therapy has shortened the
course of envenoming: prior to antivenom availability, the average length of
hospital treatment for severe bites was about 14 days. Today, antivenom-treated
patients are commonly discharged from hospital within 1 to 3 days. There have been no known deaths since
it became available.
Six-Eyed Sand Spider-Sicarius hahni. This is a medium-sized spider with body measuring 1/3 to 2/3 inch in length and legs
spanning up to 2 inches. It is a South
African living fossil that pre-dates the Gondwanaland drift some 100 million
years ago and also occurs in South America. It is found in deserts and other sandy places in southern Africa. It is a member of the Sicariidae family; close relatives may be found in both Africa and in South
America, and its near cousins, the recluses (Loxosceles), are found worldwide. Due to its
flattened stance and laterally attachéd legs, it is also sometimes known as the six-eyed
crab spider. Bites by Sciarius are uncommon; there are no proven cases and only two
suspected cases where the culprit was never identified. Sicarius bites have been experimentally shown as lethal to rabbits
within 5 to 12 hours. The genus
name Sicarius is Latin for 'murderer, from sica, a curved dagger.
This spider buries itself in the sand and strikes
from ambush at prey that wanders too closely. Sand particles adhere to cuticles
on its abdomen, thus acting .s a natural camouflage if uncovered. If disturbed,
it will run a short distance and bury itself again.
Toxicology studies have demonstrated that the venom
is particularly potent, with a powerful hemolytic/necrotoxic effect, causing blood vessel leakage,
thinning of the blood and tissue destruction.
Sicarius bite treatment
should be directed, as with all cytotoxic bites, at prevention of secondary
infection and combating disseminated
intravascular coagulation (DIC) if it develops.
Six-Eyed Crab Spider. Courtesy EcoPort
Huntsman Spiders. (Sparassidae, formerly Heteropodidae). This family is also known as the giant crab spiders, due to their appearance. Larger specimens are also
sometimes referred to as wood spiders, due to their preference for inhabiting woody places
(forest, mine shafts, woodpiles). They are known as rain spiders in southern Africa.
These eight-eyed spiders are found in Australia, New Zealand, South Africa, Southeast
Asia, the Mediterranean, Southern U.s. including Florida, and Hawaii, and
possibly in many other tropical and semi-tropical regions.
While
frequently very large they are not deadly to humans. They do bite if provoked,
but the victim will suffer only minor swelling and localized pain, and will
recover in a day or two. Some larger types resemble tarantulas, and that
term is sometimes loosely applied to them by Australians as well as the
similar-sounding slang name 'triantelope'. Huntsman spiders can generally be
identified by their legs, which, rather than being jointed vertically relative
to the body, are twisted such that the legs extend forward in a crab-like
fashion.
Australian Huntsman Spider with
Crab-Like Appearance. Image courtesy of Sklmta
Many huntsman spiders are dull shades
of brown or grey. Their legs are covered with fairly prominent spines, but the
rest of their bodies appear smooth. They are frequently found in sheds, garages
and other infrequently-disturbed places. The eyesight of these spiders is not
nearly as good as that of the Salticidae (jumping spiders). Nevertheless,
their vision is quite sufficient to detect approaching humans or other large
animals from some distance.
Members of
the huntsman family of spiders are very common in Australia, but also in many
tropical and semi-tropical parts of the world. They have been introduced to
many parts of the world, including China, Japan and southern parts of the United
States, such as Florida and Puerto Rico. A species
of huntsman can be found in Hawaii, where it is commonly known as a Cane Spider. In general
they are likely to be found wherever ships may bring them as unintended
passengers to areas that are not too cold for them to survive in the winter. A
common source of infestation is in bunches of bananas. As a result most grocers are quite familiar
with these spiders. In southern Africa they are commonly known as rain spiders
because of their tendency to seek shelter before rain storms, often entering
human habitations when doing so.
As adults,
huntsman spiders do not build webs, but hunt and forage for food: their diet
consists primarily of insects and other invertebrates, and
occasionally small skinks and geckos. They live in the crevices of tree bark,
but will frequently wander into homes and vehicles. They are able to travel extremely
fast, often using a springing jump while running, and walk on walls and even on
ceilings. They also tend to exhibit a "cling" reflex if picked up,
making them difficult to shake off and much more likely to bite. The females
are fierce defenders of their egg sacs and young. They will generally make a
threat display if provoked, but if the warning is ignored they may attack and
bite.
In general,
huntsman spiders are not regarded as dangerous, and can be considered
beneficial because they feed on insects (cockroaches are a favorite). Many
Australians will relocate huntsman spiders to the garden rather than kill them.
There have been reports of members of the genus Neosparassus (formerly called Olios) giving bites that have
caused prolonged pain, inflammation, headache, vomiting and irregular pulse
rate; however, a scientific study into the bite of these spiders did not note
any severe or unusual symptoms resulting from confirmed Neosparassus bites. It is unclear under what circumstances
these spiders bite people, but it is known that female members of this family
will aggressively defend against perceived threats to their egg sacs and their
young.
Males of Heteropoda venatoria, one of
the huntsman spiders that seems to easily find its way around the world, have
recently been found to deliberately make a substrate-borne sound when they
detect a chemical (pheromone) left by a nearby female of their species. The
males anchor themselves firmly to the surface onto which they have crawled and
then use their legs to transmit vibrations from their bodies to the surface.
Most of the sound emitted is produced by strong vibrations of the abdomen. The
characteristic frequency of vibration and the pattern of bursts of sound
identify them to females of their species, who will approach if they are
interested in mating.
The Giant Huntsman Spider (Heteropoda maxima). This is considered the world's largest spider by
leg-span. The giant huntsman spider is
the largest member of the Sparassidae, boasting a 30 centimeter (12 inches)
leg-span, and 4.6 centimeter body-length. The largest known member of the
Sparassidae known prior to the discovery of H.
maxima was the Australian Beregama aurea with a body length of about 4
centimeters.
Giant Huntsman Spider. Image Courtesy of Petra and Wilfred.
The coloration is yellowish-brown
with several irregularly distributed dark spots on the rear half. The legs have
wide dark bands before the first bend. Like all huntsman spiders, the legs of
the giant huntsman spider are long compared to the body, and twist forward in a
crab-like fashion.
The giant huntsman spider is
considered by Peter Jaeger to be a primitive species of
Heteropoda. It is found in Laos, and is probably a cave dweller because
of its pale color, long legs and special hairs on the second foot of the male.
There is no apparent reduction of the eyes, however. This may be because the
species lives by the opening of caves as well as inside them.
The giant huntsman spider was
discovered in northern Laos in 2001. During the past ten years, over a thousand
new species have been found in the Greater
Mekong Subregion. A representative of the World Wide
Fund for Nature quipped that
"Some of these species really have no business being recently
discovered," suggesting that it is surprising for a species this large to
go undiscovered for so long.
The Brown Huntsman Spider, Heteropoda venatoria. This species is found in many tropical and
subtropical parts of the world, including Asia, some Mascarene and Caribbean islands, the Southeastern US, and
(especially) Australia. In Hawaii,
where it was introduced, it is known as the cane spider. They are fairly large,
some having a leg span of approximately five inches (13 centimeters). Although
they are rather fearsome in appearance, they are very easily alarmed by the
approach of humans and will very rapidly flee.
Brown Huntsman
Spiders. Image Courtesy of Fritz
Geller-Grimm
The female
brown huntsman can be recognized by her stout body and the pillow-like egg sac
that she often carries under her. The male typically has a slender body, longer
and thinner legs, and a distinctive pattern on his carapace. Both male
and female are reddish-brown to grayish-brown in color, and slightly hairy.
Brown huntsman spiders do not spin webs. These
spiders are known to hunt by waiting quietly on a vertical surface (or even a
ceiling) and then rushing forward when their prey gets within close range.
Their exceptional agility and speed, as well as their ability to contort and
squeeze through tight spaces, give them a strong advantage both in capturing
prey and evading predators. They feed at night. Brown huntsmen are welcomed in
many homes as they feed on pests such as cockroaches and silverfish.
Web Casting Spiders. These
spiders have a unique means of capturing their prey. In this case they use a preformed web, much
like a fish-net. The spider typically builds the web over an area that is
frequented by insects such as a broad leaf, downed tree trunk or wall. The net is not sticky but are quite flexible
and can be expanded to five times its smallest size. Once the spider forms the net it move to the
desired position where it suspends on a safety line with its head facing
downward and holds the four corners of the net with its four front legs. It simultaneous holds a safety line with its
last pair of legs. When a prey passes under the spider jumps down by cutting
the safety line and simultaneous releasing the expanded tension of the
net. The net contract and entangles the
prey. Some species mark the desired target area (e.g. on a leaf below the
waiting spider) with white spots. It is
thought these serve to indicate the prey is in a good location for capture.
A web casting
spider with net in relaxed condition.
Image courtesy of Peter Chew, Brisbane Insects.
Water
Spiders. This spider as their name
implies are commonly found around slow moving streams or lakes. They are
typically long legged Figure and are capable of rapidly running over the
surface of water. Their long legs that are covered with non-wettable hairs or
setae and light body allow them to accomplish this task. They either feed on terrestrial insects or
are capable of diving below surface to catch aquatic insects, tadpoles or small
fish. Some species will actually dip or
tangle a leg into the water which is thought to either attract the above or
possibly detect subsurface movement by a potential prey.
Water Spider
SPIDER MYTHOLOGY
Because these critters are some of the larger and most commonly
encountered arthropods on the planet, it follows that there are considerable
myths and falsehoods associated with them. One very common belief in many parts
of Central and South America is that when a spider urinates on a horse, its
hoof will fall off. In such regions, children are given the task of collecting
and killing all spiders around horse corrals. In actuality, horse's hooves are
susceptible to splitting and even "falling off," which in extreme
cases leaves the animal lame for life. This phenomenon is referred to as
"founder," but is by no means due to spider pee, as spiders do not
pee and in most cases their feces is quite dry. Keep in mind that one of the
main physiological battles of these creatures is the loss of water and any
excess water in the feces would be adding to this problem. Founder can result
from any extreme tissue damage occurring on any part of the body. If this
occurs, chemical messages are produced that cause the blood vessels in the hoof
(and other parts of the body) to constrict, resulting in splitting of the hoof.
It is possible that if a horse were to be bitten by a very toxic spider (which
could cause tissue damage), founder might occur.
In some American Indian cultures, Spider Woman is a cautionary figure
used by mothers to warn unruly children. Spider Woman is a protector to the
Navajo. She instills a type of spiritual protection and, as a creator, a love
of beauty. The comparison of an intricate and elaborate orb web to a beautiful
tapestry is not hard to make. Spider Woman, being a spinner, is represented by
a tiny hole found in all traditional Navaho blankets that indicates the spot
where she can escape.
Gaia culture
portrays the spider as a sort of earth goddess, a spinner of life and death: a
positive figure. The Greco-Romans put a far darker slant to this deft weaver:
known as Arachne. Athena, the Goddess of Crafts, turns her into a spider. The
story goes that after a contest of skillful weaving, Athena is enraged by the
subject of Arachne's tapestry--a portrayal of the gods, especially Zeus
(highest god of all and Athena's father), in an unflattering light. After
condemning her to hang until dead, Athena spared her life but turned her into a
spider--dangling from a web instead of a noose. Arachne is the reason that
spiders are known as Arachnids.
Tarantulas are hairy behemoths of the American spider world. In southern
Italy, the name "tarantula" came into usage in the town of Taranto. A
local large wolf spider was considered to be extremely venomous. The legend was
that if this spider bit someone, they must begin dancing to a lively song known
as the tarantella or they would fall into a coma. The spider became known as
"tarantula." This particular spider is not really very venomous and
the others we know as tarantulas usually aren't either. But their size alone is
enough to give some people nightmares.
In Ancient
Egypt, the spider was associated with the goddess Neith in her aspect as spinner and weaver
of destiny, this link continuing later through the Babylonian Ishtar and Greek Athena. It is the story of the weaving competition
between the Greek goddess Athena and the sometimes princess Arachne. This fable
was added much later to the Greek mythos when Ovid wrote the poem Metamorphoses between AD 2-8. Arachne was the daughter of a famous Tyrian purple dyer in Hypaipa of Lydia. Due to her
father's skill with cloth dying, Arachne was adept in the art of weaving.
Eventually, she began to consider herself a greater weaver than the goddess
Athena herself and challenged the goddess to a weaving contest to prove her
skill. Athena wove the scene of her victory over Poseidon that had inspired her patronage of
Athens, while Arachne wove a tapestry featuring twenty-one episodes of infidelity
amongst the Gods of Olympus, which angered Athena. The goddess conceded that
Arachne's weaving was flawless but she was infuriated by the mortal's pride. In
a final moment of anger, Athena destroyed Arachne's tapestry and loom with her
shuttle and cursed Arachne to live with extreme guilt. Out of sadness, Arachne
hanged herself soon after. Taking pity on her, Athena brought her back to life
as a spider (using juice of aconite) after the
princess killed herself. Athena made sure that the spider retained Arachne's
weaving abilities. The Greek Arachne means "spider"
(αράχνη).
An Islamic tradition holds that during the Hijra, the Prophet Muhammad and his companion Abu Bakr took refuge in a cave whilst being
pursued by the Quraysh. The tale
goes on to say that God commanded a spider to weave a web
across the opening of the cave and a dove to construct a nest in front of it, thus deterring the
Quraish from entering (the Prophet's entry to the cave would have broken a
web). Since then, it is held in many Muslim traditions that spiders are, if not
holy, then at least to be respected.
The 10th
Century Saint Conrad of
Constance is sometimes
represented as a bishop holding a chalice with a spider in it
or over it. This refers to a story that once when he was celebrating mass a
spider fell into the chalice. Spiders were believed at that time to be deadly
poisonous, but Conrad nevertheless drank the wine, with the spider in it, as a
token of faith.
In more recent history, the famous legend of the King Robert the
Bruce of Scotland
depicts a spider as a symbol for hope. Historians are unsure of the legend's
truth but in the legend Bruce, when fighting the English, took refuge in a cave
after a series of military failures. While hiding in the cave he saw a spider,
which continued to fail to climb up its silken thread to its web. After
repeatedly failing to climb upwards, the spider eventually succeeded due to
perseverance. Taking this as a symbol for hope and perseverance, much like the
saying "try, try and try again", Bruce came out of hiding. Bruce
eventually won Scotland's independence.
The spider
has been compared with vampires as they have similar characteristics.
Both lure and ensnare prey before sucking the life out of their victim. Like
the arachnids, vampires are believed to be able to scale walls and cliff faces,
and possess fangs, similar to those of spiders.
The spider is
also depicted in various urban
legends. The daddy long legs (Pholcidae) were known as to have very potent
venom but have very short fangs to deliver the poison. The myth might have
arisen due to its similarity in appearance with the Brown
recluse spider.
However, an episode in Discovery
Channel's Mythbusters showed that a host was able to survive a bite from the
spider. Another urban myth depicts a young woman who found out that her beehive hair was infested with Black widow
spiders. An email hoax describes the attacks by the South
American Blush Spider in public toilets. The alleged spider's scientific name Arachnius gluteus literally means "butt
spider". It should be noted that the hoax spider shares some
characteristics with the two-striped
telamonia (Telamonia
dimidiata).
The spider has been featured in literature for many
centuries. In the Vedic
philosophy of India, the spider
is depicted as hiding the ultimate reality with the veils of illusion.[11] In the epic poem Ovid's Metamorphoses written about 2millennia ago. In
Chinese fantasy, Wu Cheng'en's Journey to
the West, spiders came as female monsters. They tried to eat
Xuánzŕng, but it failed. Spiders were also depicted in Dante
Alighieri's Purgatorio as the half-spider Arachne, and more recently in books such as the
fantasy novel Harry
Potter and the Chamber of Secrets by J. K.
Rowling. This
book was later followed by a motion picture of the same name, using the giant
spider Aragog from the novel as a supporting character and pet of Hagrid, a grounds
keeper in the book. Again in titles such as The Lord
of the Rings, written by J. R. R.
Tolkien, the spider takes its form as the menacing giant
spider Shelob, and was
featured in the film adaption of the last book of the Lord of the Rings series. Tolkien had previously used
spiders in his precursor to the Lord
of the Rings series with the
book The
Hobbit. In The
Hobbit, giant spiders roamed a great forested area known as Mirkwood and attacked the main characters of
the book, capturing some of them. Spiders
are a recurring theme in both Tolkien's works and in other authors. The 1952 children's novel Charlotte's
Web written by E. B. White, later made
into a feature film in 1973 and 2006, is notable
in its portrayal of the spider in a positive manner as a heroine rather than an object of fear or
horror. Atlach-Nacha is the creation of Clark Ashton
Smith and first
appeared in his short story "The Seven Geases" (1934). Atlach-Nacha
resembles a huge spider with an almost-human face. In the story, Atlach-Nacha
is the reluctant recipient of a human sacrifice given to it by the toad-god
Tsathoggua.
In graphic
novels, spiders are often adapted by superheroes or villains as their symbols or alter ego due to the
arachnid's strengths and weaknesses. One of the most notable characters in
comic book history which has taken their identity and name from the spider is
the Marvel comic book hero Spider-Man. After being
accidentally bitten by a radioactive spider, Peter Parker, later known as
Spider-Man, was able to scale tall buildings and shoot web fluid from a box
attached to his wrist. Along with these abilities came super senses and instant
reflexes. The franchise, originally created by the writer Stan Lee and artist Steve Ditko, has become
so popular that it has had three successful movies made based on the Spider-Man
comic books. Along with Spider-Man, the comic book has also introduced several
new characters using the spider as their patron: these include Spider-Woman, Spider-Girl, the Scarlet
Spider , Venom, Arańa, and the Tarantula. Many other
comic book characters have taken the guise of a spider, including Black Spider from the Batman universe, and in manga and anime; In the Pokémon franchise, Spinarak and Ariados are similar to spiders in shape; in
the Static Shockseries, Anansi the Spider takes his name and techniques from
the African trickster god.
Spiders have been present for many decades in both
film and television, predominantly in horror movies, which use them to cause
fear, especially amongst those who suffer from arachnophobia; an acute
fear of spiders. Many films have featured the spider, including: 1955'sTarantula, made in the
midst of America's fear of atomic radiation, Kingdom
of the Spiders, a 1977 film starring William
Shatner, depicts the spiders attacking humans after their
natural food supply was destroyed from pesticides; Arachnophobia, a 1990 movie in which spiders multiply in large
numbers and terrorize a group of humans; and more recently, the 2002
blockbuster Eight
Legged Freaks in which a
group of spiders is mutated from nuclear waste and attacks the nearby town via
an underground mine. Film adaptions of books featuring spiders have arisen too,
including The Lord
of the Rings: The Return of the King's Shelob and Harry
Potter and the Chamber of Secrets' Aragog, and of comic books, including the Spider-Man trilogy. In Ingmar
Bergman's film Through a
Glass Darkly, the psychotic Karin believes she has an encounter
with God in the form of a spider.
As the spider further embeds itself
into the culture of humans, more and more depictions arise: From nicknames such
as "Spider" for the Olympic skier Vladimir
Sabich, to gaming depictions such as the solitaire game Spider, to team
names such as the Cleveland
Spiders and San
Francisco Spiders to
technological mentions such as the web spider, commonly known as the web crawler. The World Wide
Web implies the
spider-like connection of information that is accessible in the Internet. Giant spiders appear in a number of role-playing
games, such as Dungeons
& Dragons and the first
edition ofWarcraft:
The Roleplaying Game, where they are described as "a
spider of staggering size—perhaps 15 feet around—with great furred body." Atlach-Nacha is an H-game that revolves around a spider demon
disguising herself as a human woman. The tarantella, a dance, is
related to the spider Lycosa
tarantula. As tattoos, spiders serve a visible
symbolic significance in popular culture. In
September 2008 a giant mechanical spider La Princesse was in Liverpool as part of a French
performing arts company spectacle. In Bionicle, the Visorak
horde are a species of six spider-like breeds, created by the Brotherhood of
Makuta in order to take over islands. They possess mutagenic venom, and spin
green, sticky webs.