Wasps

Wasps are slim-waisted, stinging insects in the order Hymenoptera. There are two main groups of wasps: the solitary wasps are relatively small parasites of other arthropods , while the social wasps are larger and live in colonies. Some other groups of tinier hymenopterans are also commonly known as wasps.

Wasps are familiar insects to most people, and they are good insects to know about because wasps can deliver a very painful sting when they feel threatened or are agitated. It is less well-known that many of the tinier species of wasps provide a very valuable service to humans because these parasites and predators can be quite effective at reducing populations of injurious species of insects.

Biology of wasps

Wasps have a complete metamorphosis with four stages in their life history : egg, larva, pupa, and adult.

Adult wasps have four sparsely veined, membranous wings, and most species have their abdomen joined to the thorax across a very narrow waist. Wasps have chewing mouth parts, useful for masticating their food and for pulping wood to manufacture the paper that wasps often use to build the cell-like walls of their nests. The ovipositor of female wasps is modified into a stinger, located at the end of their abdomen. This organ can deliver a dose of venom to kill or paralyze other insects which may be eaten or used as a living provision for young wasps. The social wasps will also aggressively sting large animals if they feel that their nest is threatened.

There are males and females of most species of wasps. However, as with most species in the order Hymenoptera, males are normally produced from nonfertilized eggs in a developmental process known as parthenogenesis . Female wasps develop from fertilized eggs and are usually much more abundant than males. In some species, male wasps are not even known to occur.

Solitary wasps are relatively small insects that build their nests in burrows in the ground or out of mud on an exposed surface. The nest is then provisioned with a insect or spider that has been paralyzed by stinging and upon which one or more eggs are laid. The prey serves as a living but immobile food for the developing larvae of the wasp. Although quite small, parasitic wasps can be rather abundant, and they can exert a substantial measure of control over the populations of their prey species.

In contrast, the social wasps are relatively large insects that live in colonies of various size. Vespid wasps develop colonies with three castes: queens, drones, and workers. The drones are relatively short-lived males and serve only to fertilize the queens. The queens are long-lived wasps, and their major function is to initiate a colony and then spend their life laying eggs. Once a colony is established, the eggs and young are tended by workers which are nonfertile female wasps that can be very numerous in large colonies. Social wasps cooperatively feed their developing young on a continuous basis, often with chewed-up insects and other animal-derived foods.

Important groups of North American wasps

The most familiar wasps to most people are the relatively large social species, such as hornets, yellow jackets, and potter wasps, all in the family Vespidae. These wasps are brightly colored, have yellow-and-black or white-and-black stripes on their abdomen, and buzz audibly when flying. Adults of these species catch insects as prey, and they also feed on nectar and soft fruits . Vespid wasps build nests out of paper, made from the cellulose fibers of well-chewed wood. These wasps sometimes attack people who have stepped on their nests
or are too close for the wasps' comfort. The stings of these large wasps, often delivered in multiple doses, can be very painful and often cause a substantial swelling of the surrounding tissue . Some people develop allergies to the stings of wasps (and bees ), and fatalities can be caused if these hypersensitive individuals are stung.

The name yellow jacket is applied to various ground-nesting species in the genus Vespula, including V. pennsylvanica in western North America and V. maculifrons in the east. The closely related bald-faced hornet (V. maculata) is a widespread and abundant species in the United States and Canada. The polistes wasp (Polistes fuscatus) builds paper nests that are suspended from tree limbs or the eaves of roofs. The potter or muddauber wasp (Eumenes fraterna) makes clay nests suspended from branches of trees and shrubs.

The spider wasps (family Pompilidae) build their nests in the ground and provision them with paralyzed spiders. One of the better-known species is the tarantula wasp (Pepsis mildei) which is famous for its skills at hunting and subduing tarantula spiders which are much larger than the wasp. Virtually all tarantulas that are located by a tarantula wasp become living pantries for the young of these efficient predators.

Chalcid wasps are various, minute-bodied species of parasitic wasps in the superfamily Chalcidoidea made up of several families. Adult chalcid wasps feed on nectar, plant juices, or honeydew, a sweet secretion of aphids . The young wasps, however, are reared in the bodies of arthropods, usually eventually killing the host. Some species of chalcid wasps are bred in captivity in enormous numbers and are then released into fields or orchards in an attempt to achieve a measure of biological control over important insect pests . For example, the trichogramma wasp (Trichogramma minutum), only 0.1 in (2.5 mm) long, will parasitize more than 200 species of insects. This useful wasp has been captive-reared and released to reduce populations of bollworms of cotton , corn earworms, and spruce budworms in conifer forests .

Resources

books

Arnett, Ross H. American Insects. New York: CRC Publishing, 2000.

Borror, D. J., C.J. Triplehorn, and N. Johnson. An Introduction to the Study of Insects. New York: Saunders, 1989.

Carde, Ring, and Vincent H. Resh, eds. Encyclopedia of Insects. San Diego: Academic Press, 2003.

Ito, Y. Behaviour and Social Evolution of Wasps. Oxford, England: Oxford University Press, 1993.

Ross, K.G., and R.W. Matthews, eds. The Social Biology of Wasps. Ithaca, NY: Cornell University Press, 1991.

Wilson, E. O. The Insect Societies. Cambridge, MA: Harvard University Press, 1976.

Bill Freedman

KEY TERMS

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Biological control

—The use of a nonpesticidal biological method to control the abundance of a pest. Parasitic and predatory wasps are sometimes used to achieve a measure of biological control of some pest insects.

Parthenogenesis

—Reproduction by the development of an unfertilized gamete. In wasps, unfertilized eggs develop into males.