This diverse order contains a large group of insects that are closely related to the Hemiptera. Even though there is tremendous variation in the overall appearance of homopterous insects, all are phytophagous. The mouthparts are similar to those of Hemiptera; they are piercing-sucking with four piercing stylets (mandibles and maxillae). The beak rises from the back of the head; in some cases it almost appears to arise from between the front coxae (first segments of the legs). The order name Homoptera refers to the front wings being either uniformly membranous or uniformly leathery (homo = same, ptera = wings).
South American Species of Plant Hopper with Leathery Front Wings. Image Compliments of Entophiles.
Aphids. These tiny insects are easily recognized by a teardrop shaped body and the presence of tailpipe appearing structures (cornicles) emerging from the top of the sixth abdominal segment. The cornicles excrete a variety of noxious chemicals that are intended to repel the large variety of insects that feed on them.
Colony of Aphids. Image Courtesy Michel Vuijlsteke Creative Commons BY CC 3.0 Unported.
These insects may be winged or non-winged as adults. As with all homopterous insects, aphids suck plant sap from stems, leaves and roots. In many species, this feeding results in a distortion or curling of the leaves. Subsequently, aphids frequently are found in the curled-up leaves, thus avoiding possible predators.
Aphids secrete large amounts of honeydew. They feed on plant sap that is high in sugars but low in nitrogen. Since they need more nitrogen than provided by normal feeding, they suck excessively and excrete the excess sugars through the anus in the form of a clear, sticky, partially digested sap called honeydew. Some aphids excrete their own body weight in honeydew every hour. Honeydew producing insects normally have a symbiotic relationship with ants; that is, a relationship where both parties benefit. Ants are drawn to aphids and frequently tend or 'milk' them for the honeydew. They frequently will approach an aphid from behind and first stroke one side of the abdomen with their antennae and then the other side. Soon a drop of honeydew is expelled and subsequently consumed by the ant. The ant's benefit is obvious because the honeydew is food. Aphids also benefit from the presence of the ants. Aphids are vulnerable to a large number of predators and parasitoids. The activity of the ants keeps the aphid-eating insects away. They rarely eat the aphids but readily attack these predators and parasitoids.
Some ant species carry this mutualistic relationship to extremes. They may herd, push or carry the aphids to the terminal ends of the plants where growth is new and more nutritious plant sap is found. The result is an increase in the quantity and quality of honeydew. There are even a few species that will carry their “pets” from plant to plant in search of better feeding locations. With the threat of rain, ants will also round up their aphids and places them in groups under large leaves. Some species of ants build igloo-like shelters out of bits of debris over individual aphids. They leave enough room at the top of these structures to tend the aphids for honeydew but not enough for the aphids to escape. This insures the ants a constant source of food and protects the aphid from predators and parasites. It is well established that ants are the only species of animal that is known to keep pets besides humans.
During the winter months, when little or no plant sap is available, there is one species of ant that will collect the eggs of aphids and take them to their nest below ground. In the spring when plants begin to grow again, the eggs are removed from the nests and placed on the plants; they subsequently hatch to produces aphids that soon begin production of honeydew.
Amazingly, the news queens of a few ant species carry honeydew producing scale insects in their mandibles when they depart from the nest on their nuptial flight. After mating and settling to the ground, they are ready to start a new colony with the start of a food source, namely the honeydew producing scales.
The most complete and remarkable symbiotic relationship between an ants and honeydew producing insects was first discovered in 1980. This species of rainforest ant feeds entirely on honeydew produced by a species of mealybugs. The mealybugs are carried to and from the ants nest to certain trees and shrubs that are as far away as 60 feet. The ants do little conventional nest building but locate preformed cavities in dense brush or trees. Much of the perimeter walls of the nests are formed by the ant’s bodies, much like what occurs with army ants. They cling to one another to create a solid mass that shields their own brood and of course the mealybugs. A fully developed colony contains a single queen, over 10,000 worker ants and about 9,000 mealybugs. The transport of the mealybugs between the two sites is intense: at any time as much as 10 % of the worker ants are carrying mealybugs in their mandibles. The location of the ant’s nest is by no means permanent. If necessary, ants will readily move a nest to a new location. These ants are true nomadic ranchers -but in this case the stock is mealybugs instead cattle and the ranchers are ants.
Some aphids that depend on ants for their protections have acquired structural and behavioral adaptations. These typically have smaller or lack cornicles; therefore they may lack the defensive chemicals produced by these insects. In addition, they have a thinner protective coat of waxes on the outside of their bodies than do aphids that are not tended by ants. Aphids that are not typically tended by ants forcibly propel honeydew drops well away from their body. This behavior keeps them free from this sticky-gummy liquid and the fungus that develops upon it. On the other hand, tended aphids gently oozes the honeydew from there anus making it readily available to ants. Many have a basket of hairs around the anus to hold the honeydew in place until consumed. If not readily consumed by an ant, the honeydew is even withdrawn back into the aphid until a later time.
Honeydew can cause problems on plants. A black sooty mold or fungus quickly develops on honeydew that accumulates on leaves and fruit. This mold does not normally directly harm the leaves, but a heavy infestation will block sunlight from reaching the leaf surface, thereby reducing photosynthesis. This can severely reduce the plant’s growth and vigor. In addition on ornamental plants, this black fungus greatly reduces the aesthetic value of the plant.
Aphids have an extremely efficient and somewhat unique mode of life. Most aphids overwinter in the egg stage on a primary host. In the springtime, the eggs hatch and quickly develop into wingless females that reproduce parthenogenetically. That is, the female produces her offspring, all of which are female without fertilization of the eggs. Aphids are also ovoviviparous. This means the eggs are maintained inside the body until hatching and the female gives birth to the first instar nymphs. For generations, the wingless females live on the primary host plants. For example in one of the most common species, the green peach aphid, the primary host tree is the genus Prunus sp. (e.g. peach, plum. prune). Once the primary host becomes crowded with aphids, the physical closeness of the females triggers a physiological reaction where the next generation developing wings. Subsequently, they swarm or leave the primary host in the spring and fly to any of a few hundred species of secondary host plants. Many generations live in the summer months on these plants; again, only females are produced parthenogenetically and the young are born alive. In the fall, the females migrate back to the primary host, mate with males and lay eggs. Males represent a small portion of the overall population with a few females mating through the spring and summer months. This insures that some males will be available. Aphids have a tremendous reproductive capacity. One female is capable of producing several hundred offspring within a two-week period.
Control. Aphids would be a great deal more destructive were it not for the numerous predators and parasitoids that attack them. One of the most effective means of controlling aphids is ant control. If ants can be prevented from protecting aphids, the beneficials (predatory insects) will quickly reduce an existing aphid population. There are various insecticides that can be used to control aphids. There are many plant extracts and plant products that are eco-friendly and control aphids as effectively as more standard chemical insecticides. For small backyard infestations, simply spraying the plants thoroughly with a strong water jet every few days is sufficient protection for roses and other plants.
Cicadas. Members of this family are recognized by their shape and large size. This group contains the largest Homoptera in the world, with some Southeast Asian species approaching four inches in length and a wingspan of 8 inches. Cicadas can produce the loudest sound in the insect world. The males produce this song when approaching a female for mating. The male’s sound is produced by vibration of organs (tympana) located on the underside of the thorax. Cicadas generally are quite long-lived. The eggs are deposited in twigs and stems; once hatched, the nymphs drop to the soil, form a cavity below ground, and feed on the roots of plants. The nymphal stage is slow to develop and requires from one-to-seventeen years to reach adulthood. Once fully developed the nymphs emerges from the ground, crawls up vegetation Cicadas are sometimes called locusts. The seventeen-year locust is one of our longest lived insects. Typically, most adult cicadas live for a few months.
In the jungles of Southeast Asia during the mating season, the simultaneous singing of thousands of cicadas can be almost deafening. Cicadas also produce a 'protest' squeak’ when handled. This is unquestionably a defensive mechanism used against attacking predators.
Left. Sequence of Ault Cicada Emerging from Nymph (upper left corner) to Drying and Expanding Wings to Empty Nymphal Exoskeleton (bottom right). Public Domain. Courtesy Jim DeWitt.
The Membrane-like Tympana of Male Cicadas. Image Dr. Kaae.
Periodical Cicada. Image Dr. Kaae.
Seventeen Year Locust. The most notorious species is the periodical or seventeen-year locust. There are two forms of this species with one completing its life cycle in 17 years and the other in 13 years. These cicadas occur primarily in the eastern and southern United States. Certain years, huge numbers of these pests emerge from the soil in the spring causing considerable damage. Magicicada spp. spend most of their 13- and 17-year lives underground feeding on xylem fluids from the roots of deciduous forest trees in the eastern United States. After 13 or 17 years, mature cicada nymphs emerge in tremendous numbers. After such a prolonged developmental phase, the adults are active and for about 4 to 6 weeks. The males aggregate into chorus centers and attract females. Within two months of the original emergence, the life cycle is complete, the eggs have been deposited and the adult cicadas are gone for another 13 or 17 years.
Periodical Cicada Adults and Nynphal Exoskeletons. Image Courtesy http://community.webshots.com/album/142722205TnsfdE/2]. Photo by Arthur D. Guilani
The adult periodical cicada has red eyes and a black dorsal thorax. The wings are translucent and have orange veins. The underside of the abdomen may be black, orange, or striped with orange and black. Adults are typically 2.4 to 3.3 cm (0.9 to 1.3 inches) in length. Different species have different characteristic calling songs. The call of the decim periodical cicadas is said to resemble someone calling "weeeee-whoa" or "Pharaoh." The cassini and decula periodic cicadas have songs that intersperse buzzing and ticking sounds.
Cicadas do not typically bite and cannot sting. They have mouthparts used in piercing plants and sucking their sap. A cicada's proboscis can also pierce human skin when it is handled. This is painful but in no other way harmful. These cicadas are not venomous, and there is no evidence that they transmit diseases. They pose little threat to mature vegetation, although planting new trees or shrubs is best postponed until after an expected emergence of the periodical cicadas. Mature plants rarely suffer lasting damage, although twig die-off or flagging can result from egg-laying.
The nymphs emerge on a spring evening when the soil temperature at about 8 inches depth is above 63 °F. In most years, this works out to late April or early May in far southern states and late May to early June in the far northern states. Emerging nymphs climb to a suitable location on the nearby vegetation to complete their transformation into an adult cicada. They molt one last time and then spend about six days in the leaves waiting for their exoskeleton to harden completely. Just after this final molt, the adults are white, but darken within an hour.
The nymphs emerge in large numbers at about the same time. Sometimes there are more than 1.5 million individuals per acre (about the size of a football field). Their mass-emergence is a survival trait called predator satiation: for the first week after emergence, the periodic cicadas are an easy prey for reptiles, birds, squirrels, cats, and other small and large mammals. It was originally thought that the cicadas' overall survival mechanism was simply to overwhelm predators by their sheer numbers, thus ensuring the survival of most of the individuals. It was hypothesized that the emergence period of large prime numbers (13 and 17 years) was a predatory avoidance strategy adopted to eliminate the possibility of potential predators receiving periodic population boosts by synchronizing their own generations to divisors of the cicada emergence period.
Cycles in cicada populations are significant enough to affect other animal and plant populations. For example, tree growth has been observed to decline the year before the emergence of a brood. It is postulated that this is due to the increased feeding on roots by nymphs. Moles which feed underground on nymphs have been observed to do well during the year before an emergence, but suffer population declines the following year. Wild turkey populations respond favorably to increased nutrition in their food supply from gorging on cicada adults on the ground at the end of their life cycle. Uneaten carcasses of periodic cicadas decompose on the ground and provide a resource of nutrients to the forest community.
Reportedly because of global warming the 17 year locusts are emerging from the soil 2 years early. This makes total sense because the main factor that determines how fast an insect completes its life cycle is temperature. The hotter the temperature, the faster is an insect’s life cycle. Plus 1 for global warming!