Hymenoptera

(invertebrate zoology) A large order of insects including ants, wasps, bees, sawflies, and related forms; head, thorax and abdomen are clearly differentiated; wings, when present, and legs are attached to the thorax.

(Sawflies, ants, bees, and wasps)

Class: Insecta

Order: Hymenoptera

Number of families: About 84

Evolution and systematics

Hymenoptera is a worldwide order of at least 100,000 described species, more biologically diverse than any other insect order. The order is divided into two suborders— Symphyta (wood wasps and sawflies) and Apocrita (wasps, bees, and ants)—with 22 superfamilies and about 84 families. The fossil record dates from the Triassic (245–210 million years ago). The Hymenoptera may be the sister group of the Antliophora, made up of Diptera (flies), Siphonaptera (fleas), and Mecoptera (scorpionflies and hangingflies); and the Amphiesmenoptera, comprising the Trichoptera (caddisflies) and Lepidoptera (butterflies and moths).

Physical characteristics

Adult hymenopterans range in size from minute to large, at 0.006–4.72 in (0.15–120 mm) and from slender (e.g., many wasps) to robust (e.g., the bumble bees). The head usually is very mobile. The compound eyes often are large and sometimes strongly convergent dorsally. Fine setae occasionally emerge from between facets, and ocelli may be present, reduced, or absent, especially in forms with reduced wings. The antennae are long and multisegmented, and their surfaces are covered with various sense organs. The mouth-parts vary from the generalized biting type to the combined sucking and chewing type (e.g., bees). Mandibles typically are present and are used by the adult to cut its way out of the pupal cell, for defense, for killing and handling prey, and in nest construction.

The first abdominal segment of the Apocrita is attached firmly to the metathorax and usually is separated from the remaining abdominal segments (metasoma) by a narrow waist (petiole). In Apocrita thoracic segments plus the first abdominal segment are called the mesosoma, and the incorporated first abdominal segment is the propodeum, followed by the remainder of abdomen. There are generally two pairs of wings. Venation is most complete in Symphyta and mostly reduced in small Apocrita. The hind wings have rows of hooks (hamuli) along the leading edge that couple with the hind margin of the forewing in flight. The legs frequently are cursorial (adapted for running), sometimes with fossorial (adapted for digging) forelegs; the hind legs are modified to carry pollen.

Sensory structures (sensilla) on the ovipositor enable the female to recognize suitable egg-laying sites. In some ants, bees, and wasps the ovipositor has lost its egg-laying function and is used as a defensive, venomous stinger. Although the smooth stingers of ants and wasps allow for repeated use, the barbed stings of the honeybee can be used only once. As the honeybee struggles to leave the stinger and venom behind, it is disemboweled and soon dies.

Bees have several morphological adaptations associated with pollen collection, including plumose (branched) hairs. Moreover, the hind tibia and basitarsus are enlarged, with long hairs on their outer surfaces. These hairs either form a brush (scopa) or are reduced to a fringe surrounding a bare area or concavity (corbicula, or pollen basket). Leaf cutter bees have a well-developed scopa on the ventral surface of the abdomen.

Distribution

Hymenopterans are found worldwide.

Habitat

Hymenoptera occur in soil and litter or on vegetation. Most are active on bright, sunny days, hunting insects, gathering pollen and nectar, or assembling nest-building materials. Some parasitic species are active at night, when their nocturnal hosts are active.

Behavior

Symphyta lay their eggs on or in leaves, stems, wood, and leaf litter, and females sometimes stand guard over their egg masses. The larvae are almost exclusively phytophagous. Pupation takes place within the plant tissue or in the ground. Most have a single generation a year and overwinter as full-grown larvae. The larvae of many species of Apocrita are parasitoids in the immature stages of other insects (or other invertebrates), while the adults are free living.

Idiobiont parasitoids prevent any further development of the host after initial parasitization. Koinobiont parasitoids allow the host to continue its development and often do not kill and consume the host until the host has reached its maximum size. The development of a secondary parasite, or hyperparasite, at the expense of a primary parasite is more frequent in Hymenoptera. The Apocrita species that have the ovipositor modified into a sting are grouped together into the Aculeata. Female Scoliidae locate and attack large subterranean beetle larvae in their burrows or earthen pupal cells. The sting does not kill the host but only immobilizes it. Then the female lays her eggs and departs, leaving her offspring to develop without further assistance. Aculeate hymenopterans may or may not use their stings to immobilize the host; mutillids bite through the host cell and lay an egg on the mature larvae or pupae of the host.

Somewhat more complex behavior is exhibited by many Pompilidae, in which the female captures and paralyzes her prey and then drags it to a cavity or crevice on the ground. She lays an egg on the host and usually seals the cavity before leaving. Cleptoparasites, such as cuckoo bees of the genus Chrysis (actually a metallic blue or green, thick-bodied wasp), construct no nests of their own and instead rely primarily on the food stores of hosts (Chrysis). In other aculeates (for example, other Pompilidae), the female wasp prepares a nest before locating prey and can relocate her nest when she returns with prey.

Female Eumenes (Vespidae) lay eggs in the empty cell before prey are introduced. The female then provides the cell with prey and seals it before the larva begins to develop. This is called mass provisioning, because the initial food that is amassed must be sufficient to feed the larva during the entire course of its development. Progressive provisioners, such as many Sphecidae and Vespidae, provide additional food at intervals. Large, multicelled nests, in which each cell is stocked with many small prey, are characteristic of many behaviorally advanced species. Bees (Megachile and Xylocopa) are similar to wasps in this respect, except that they provision larval cells with pollen and nectar rather than arthropod prey.

Truly social or eusocial hymenopterans have a division of labor, with a caste system involving sterile individuals that assist the reproducers, cooperation among colony members in tending the young, and overlap of generations capable of contributing to colony functioning. Among hymenopterans exhibiting primitive eusociality are paper wasps. The highly eusocial hymenopterans comprise the ants, some wasps, and many bees. Common construction materials for nest building are mud, leaves, and masticated wood chips that are formed into a paper- or carton-like nest.

Feeding ecology and diet

Adult parasitoids require carbohydrates in the form of honeydew, nectar, or other plant secretions. Many female parasitoids also feed extensively on the body fluids of hosts, to sustain egg production. Most symphytan larvae are phytophagous (plant eaters); larvae of Siricidae are wood borers and utilize cellulases produced by fungi to feed on wood; the enzymes necessary for processing the wood fragments are acquired from the fungus ingested. Apocritan larvae have diverse feeding habits; they may be parasitic or gall forming, or they may be fed with prey or nectar and pollen by their parents or other colony members. Adult hymenopterans mostly feed on nectar, pollen, or honeydew produced by Homoptera; only a few consume other insects. Many wasps feed their young macerated or paralyzed insects and spiders. Most bees feed young pollen and nectar. Many members of the order visit flowers for nectar or pollen. Leaf cutter ants feed on fungi, which they cultivate in the nest. The ants live in an obligate mutualistic association with a fungus. The fungus has lost its capacity for sexual reproduction; dispersal occurs by means of the queen ant carrying fungal hyphae to a new nest site.

Reproductive biology

Males of parasitic species commonly search for females at their emergence sites and occasionally fight for possession of such sites. Some males form female-attracting swarms. Among most hymenopterans the females produce pheromones, chemicals that attract and sexually stimulate males of the same species. Courtship in the Apocrita is common and complex, involving sequences of antennal contact, leg and wing vibrations, and mandibular movements. Sex in most Hymenoptera species is determined by the fertilization of the egg; fertilized eggs develop into females, and unfertilized eggs usually develop into males. Thus, females determine the sex of their offspring and can manipulate the rate of increase of their populations.

The adult female searches for a host by responding to a series of cues in the environment. When she locates a potential host, she examines it often with her antennae or the tip of the ovipositor, to decide whether it is acceptable as a site for egg deposition. Females of some species lay their eggs on a broad range of similar hosts within a particular habitat, whereas others are highly specific to a single host or a few closely related species. Most parasitoid species lay their eggs on or in the body of the host, and many have a long ovipositor to reach hosts in cocoons, burrows, or other protected situations. In some cases only a single egg is laid on a host (solitary parasitism); in others, several to many eggs may be laid on the same host (gregarious parasitism). The larva may be ectoparasitic, that is, developing externally, or endoparasitic, developing within the host. Sometimes early instars are endoparasitic, and later instars are ectoparasitic. Pupation typically occurs within or beside the host remains.

Hymenoptera are holometabolus insects, that is, they have a life cycle progressing from egg to larva to pupa to adult. The eggs are ovoid or sausage-shaped, with a respiratory stalk in some parasitic species and with hooklike or sucker-like attachment devices in some ectoparasites. The outer covering typically is thin and smooth, sometimes with little yolk. Polyembryony, that is, development of several individuals from one egg, occurs in some parasitic species.

In Symphyta the larva is eruciform. The head is well sclerotized, and there are three pairs of thoracic legs and abdominal prolegs (commonly on the second through eighth and the tenth abdominal segments). There are as many as eight larval instars, with females often having one more than males. In Apocrita the larva is vermiform, apodous, grublike, or maggot-like, and the head capsule is weakly sclerotized. Primitively, they probably have five larval instars, but the number is reduced in many endoparasitoids.

Larval heteromorphosis occurs in many parasitic species. In these species, whereas the final instar larva is vermiform, the first or intermediate instars are of diverse forms. Pupae of the exarate type have free appendages that are not glued to the body; they may form in a cocoon in the host or in special cells. The cocoon is spun with silk from the labial glands. Some hymenopterans may spend a very long period in diapause within the cocoon.

Conservation status

The 2002 IUCN Red List includes 152 hymenopteran species. Of these, 3 are listed as Critically Endangered; 142 as Vulnerable; 6 as Lower Risk/Near Threatened; and 1 as Data Deficient.

Hymenopterans are susceptible to the indiscriminate use of insecticides and to habitat destruction. The effects of insecticides include the eradication of nontarget organisms, including such pollinators as bees and wasps. Without the pollinating services of bees and other insects, we would have few vegetables, fruits, and flowers and little or no clover. To achieve preservation of these key aspects of our lives, hymenopteran biotopes must be conserved and utilized in a sustainable fashion.

Significance to humans

Certain hymenopterans were considered deities in such civilizations as Egypt. To the Greeks the bee Melitta was known as the Goddess Honey Mother. The ant-hunting species of Dinoponera was a symbol of virility for several Amazon tribes and was used in initiation rituals. The Mixe people of Oaxaca (Mexico) believe that they become more powerful through the ingestion of ants; ants thus have come to stand for virility, fortitude, and courage. The bee Melipona beechei in Mexico represented the spiritual world, merriment, and rain. Wasps and bees are represented frequently in literature, music, theater, cinema, and television. The Greek comic playwright Aristophanes, for example, wrote a play called The Wasps, satirizing the Athenians' love of litigation and characterizing jurors as wasps in their harshness. The Russian composer Nikolai Rimski-Korsakov, inspired by the sound that bees produce, composed the "Flight of the Bumblebee," a piece of music for strings set within the opera The Tale of Tsar Saltan, the story of a prince who is turned into a bee. In modern times, several protagonists of the Pokemon cartoons represent hymenopterans.

From the standpoint of human beings, Hymenoptera probably is the most beneficial order of insects; it contains many insects that are of value as parasitoids or predators of other arthropods, including insect pests. They have been employed successfully as pest control agents in several countries. Bees generally are regarded as the most important group of insect pollinators. Apis mellifera is of great commercial value as a producer of honey that is used extensively as food and in the manufacture of many products. Beeswax is used in making candles, sealing wax, polishes, certain types of ink, models of various kinds, and in other products such as face and hand creams, lipsticks, and lip salves.

Nest-building Hymenoptera can be domestic nuisances. Bees and wasps inject venom when they sting. Many people are highly sensitive to bee or wasp stings and may suffer anaphylactic shock leading to death or disability as the result. The sting of the female hymenopteran can seem unprovoked, but it is, in fact, an aggressive defense of the nest.

Hymenopterans are food for humans in some parts of the world. They are edible at all stages of growth. Boiling tends to break down the poison, which is basically protein and, at boiling temperatures, the stinger softens. Pounding them before boiling makes them more edible. Ants (except the fire ant) and ant larvae are edible and tasty. Australian aborigines living in arid regions derive sugar from species of Melophorus and Camponotus, popularly known as honey pot ants. Specialized worker ants (repletes) are fed with nectar by other workers and store it in their huge distended crops. Honey pot ants in the western United States and Mexico belong to the genus Myrmecocystus.

Few species of Hymenoptera are harmful. Sawfly larvae cause damage to forests, orchards, and ornamental trees. Wood-boring larvae, in association with fungi, can cause extensive damage to plantations of conifers. A few ants are pests, for example, the leaf cutter ants or the seed harvesters; others protect sap-sucking insects, which are pests themselves.

Species accounts

Resources

Artigas, Jorge N. Entomología Económica: Insectos de Interés Agrícola, Forestal, médico y Veterinario. 2 vols. Concepción, Chile: Ediciones Universidad de Concepción, 1994.

Borror, Donald J., Charles A. Triplehorn, and Norman F. Johnson. An Introduction to the Study of Insects. Philadelphia:W. B. Saunders, 1989.

Clausen, C. P. Entomophagous Insects. New York: Hafner, 1972.

Correa-Ferrêira, B. S. Utilizaçao do Parasitóide de Ovos Trissolcus basalis (Wollaston) no Controle de Percevejos da Soja. Centro Nacional de Pesquisa de Soja, Circular Técnica no. 11. Londrina, Brazil: EMBRAPA Soja, 1993.

Costa-Neto, Eraldo M. Manual de Etnoentomología. Manuales & Tesis Sociedad Entomológica Aragonesa (SEA) 4. Zaragoza, Spain: Sociedad Entomológica Aragonesa, 2002.

CSIRO, eds. The Insects of Australia: A Textbook for Students and Research Workers. Carlton, Australia: Melbourne University Press, 1991.

Danks, H. V., and J. A. Downes, eds. Insects of Yukon: Biological Survey of Canada (Terrestrial Arthropods). Ottawa, Canada: Canadian Museum of Nature, 1997.

De Santis, L., and P. Fidalgo. Catálogo de los Himenópteros Calcidoideos de América al Sur de los Estados Unidos. Serie de la Academia Nacional de Agronomía y Veterinaria no. 13. Buenos Aires, Argentina: Editorial Hemisferio Sur, 1994.

Gullan, P. J., and P. S. Cranston. The Insects: An Outline of Entomology. Oxford and Malden, MA: Blackwell Science, 2000.

Hanson, P. E., and I. D. Gauld. The Hymenoptera of Costa Rica. Oxford: Oxford University Press, 1995.

Hölldobler, Bert, and Edward O. Wilson. The Ants. Cambridge, MA: Harvard University Press, 1990.

Samways, M. J. Insect Conservation Biology. London and New York: Chapman and Hall, 1994.

Johnson, N. F. Catalog of World Species of Proctotrupoidea, Exclusive of Platygstridae (Hymenoptera). Memoirs of the American Entomological Institute no. 51. Gainesville, FL: American Entomological Institute, 1992.

Llorente Bousquets, Jorge, and Juan J. Morrone, eds. Biodiversidad, Taxonomía y Biogeografía de Artrópodos de Mexico: Hacia una Síntesis de su Conocimiento. Mejicana. Vol.3. Mexico: Universidad Autónoma de México, 2002.

Loiácono, M. S., N. B. Diaz, and L. De Santis. Estado Actual del Conocimiento de Microhimenopteros Chalcidoidea, Cynipoidea, y "Proctotrupoidea" en Argentina. Monografías Tercer Milenio, vol. 2. Zaragoza, Spain: Sociedad Entomológica Aragonesa (SEA) & CYTED, 2002.

Vardy, C. R. The New World Tarantula-Hawk Wasp Genus Pepsis Fabricius (Hymenoptera: Pompilidae). 2 parts. Backhuys. Netherlands: Zoologische Verhandelingen, 2000–2002.

De Santis, L. "Catálogo de los Himenópteros calcidoideos de América al Sur de los Estados Unidos." Second supplement. Acta Entomológica Chilena 15 (1989): 9–90.

De Santis, L., and N. P. Ras. "Control Biológico de la Cochinilla Phenacoccus manihoti en África (Insecta)." Academia Nacional de Agronomía y Veterniaria 42, no. 7 (1988): 5–11.

Johnson, N. F. "Systematics of New World Trissolcus (Hymenoptera: Scelionidae): Species Related to T. basalis)." Canadian Entomologist 117, no. 4 (1985): 431–445.

Johnson, N. F., and L. Musetti. "Revision of the Prototrupoid Genus Pelecinus Latreille." Journal of Natural History 33 (1999): 1513–1543.

Kempf, W. W. "Catálogo Abreviado das Formigas da Regiao Neotropical." Studia Entomologica 15 (August 1972): 3–334.

Loiácono, M. S., and C. B. Margaría. "Ceraphronoidea, Playgastroidea, and Proctotrupoidea from Brazil (Hymenoptera)." Neotropical Entomology 31, no. 4 (2002): 551–560.

"Chrysis.net" [May 6, 2003]. "Avispa Taladradora de la Madera. Sirex noticlio Fab." [May 6, 2003]. . "Apoidea" [May 6, 2003]. .

Biblioteca de Atualizaçao. Ciêcias Entendendo a Natureza. "Vespa contra Vespa um Exemplo de Controle Biológico" [May 6, 2003]. . "Chapter 1: Honeybees of the Genus Apis" [May 6, 2003]. . "European Wood Wasp, Sirex noctilio F.—Siricidae" [May 6, 2003]. .

The Natural History Museum. "Bombus " [May 6, 2003]. . "Wild West Yorkshire Nature Diary: Ducks on the Water" [May 6, 2003]. .

[Article by: Marta Loiácono, DSc; Cecilia Margaría, Lic]

The third largest order of insects, containing the sawflies, ants, wasps, bees, and related forms. Conservative estimates suggest that the world fauna may comprise well over 100,000 described species of this order, with many thousands still to be described. See also Insecta.

This order is of great importance to humans. Some members such as the sawflies, certain chalcidoids, and most cynipoids, feed during the larval stage on foliage or other plant tissues. Many species, such as the ichneumon flies, most chalcid flies, and wasps, are parasites or predators of other insects or spiders during their larval stage. Bees are indispensable in the pollination of many fruits, vegetables, and forage crops. See also Bee.

Hymenoptera occur in all major faunal zones but are more abundant and have greater diversity of species in the tropical and temperate zones.

Adult Hymenoptera usually may be recognized by having two pairs of membranous wings with reduced venation, the hind pair smaller than the front pair, and by mouthparts formed for biting and often for lapping or sucking. In the higher forms, the abdomen is constricted basally, its first segment fused with the hind part of the thorax. Females always have an ovipositor modified for sawing, piercing, or stinging. Metamorphosis is complete.

The first four superfamilies of the Apocrita—the Ichneumonoidea, Chalcidoidea, Cynipoidea, and Proctotrupoidea—are commonly called the Parasitica, and the remaining super-families are known as the Aculeata. The Aculeata are stinging forms and the Parasitica are parasites of other insects. It is impossible to demarcate these two groups sharply because some Aculeata are parasites and some Parasitica are phytophagous. However, except for the phytophagous species of Parasitica, these insects lay their eggs in or on an insect or spider host while the Aculeata place theirs in nests with a provision of food. The table presents the major classification of the order as recognized in North America.

Morphology

The adult hymenopteran has a clearly differentiated head, thorax, and abdomen. Wings, when present, and legs are attached to the thorax.

Typically the head is so oriented that mouthparts are directed downward; however, all variations occur, and in some species the mouthparts are directed forward. The large compound eyes occupy much of the sides of the head, though they are reduced in size in many ants and some Parasitica. Three ocelli are typically present on the top of the head, but may be reduced or absent in wingless forms. The paired antennae arise from the face between the eyes, and they may be close to the mouthparts or removed from them.

The thorax consists of three segments, tightly fused together. Each segment bears a pair of legs, and each of the last two segments bears a pair of wings. In flight, the fore- and hind-wings are joined by a row of tiny hooks along the fore margin of the posterior wing, which fit into the downfolded hind margin of the anterior wing. Flightless species with shortened, nonfunctional wings, or no wings at all occur in most major groups, except the sawflies and bees.

The abdomen primitively consists of 10 segments, though the number appears to be less because of modification or loss in the higher forms. The female ovipositor, or sting, is formed from processes of the eighth and ninth sterna.

In the Apocrita there is a pair of acid glands opening into a poison sac connected with the ovipositor. The secretion of these glands produces either a temporary paralysis when injected into their hosts by some Parasitica, or, usually, permanent paralysis when injected into their prey by aculeate wasps. Bees use their stings purely for defense. When a human is stung, the enzymes react with the tissues to release histamine. Death may occasionally result from anaphylactic shock, or from mechanical suffocation due to swelling of the lymphatic system. Medical assistance should be sought if severe swelling occurs following a sting, especially one on the face or throat.

Biology

Practically all hymenopterous adults are terrestrial forms, living in, on, or near the Earth's surface. A few species are secondarily aquatic, the adults swimming or walking under water to search out and parasitize aquatic or subaquatic hosts.

Most adults feed on plant nectar or honeydew secretions of various insects. A few sawflies prey on other insects. Some species of Parasitica and Aculeata imbibe body juices of the host or prey which they attack primarily for oviposition.

Mating takes place in a variety of situations, but it is always of rather short duration. Most species are represented by both males and females. Males are usually produced from unfertilized eggs and have half the normal number of chromosomes, while females are produced from fertilized eggs and have the normal number of chromosomes.

Hymenoptera exhibit complete metamorphosis during development and pass through an egg, larval, and pupal state. So far as is known, Hymenoptera always lay eggs. These are deposited in a protected situation on or near the supply of larval food. The hymenopterous egg is usually ovoid or sausage-shaped, and many species in some groups have stalked eggs.

Some species have only one generation a year in temperate zones, others have two, and many breed continually during the warmer months. Hymenoptera usually overwinter as prepupae but occasionally ants, social wasps, and some bees overwinter as adults or as larvae, as in some Parasitica.

Sexual dimorphism is often very marked. The two sexes of some species are so dissimilar that earlier students placed them in different genera or families. Even today there are many puzzles, and sexes have not been associated for many of the species having wingless females and winged males. Ordinarily the males are somewhat smaller than females, though the reverse is true in most species having wingless females. See also Sexual dimorphism; Social insects.

An order of the class Insecta. Includes the ants, wasps, hornets, bees, fireants and sawflies. Characterized by two pairs of shiny, membranous wings.

• h. sting — a cause of injury and sometimes serious toxic and hypersensitivity reactions, particularly in dogs, which may be local or systemic. See also bee sting.

Look up Hymenoptera in Wiktionary, the free dictionary.

Hymenoptera Fossil range: 251–0 Ma PreЄ Є O S D C P T J K Pg N Triassic - Recent
female Netelia producta
Scientific classification
Domain:	Eukarya
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Subclass:	Pterygota
Infraclass:	Neoptera
Superorder:	Endopterygota
Order:	Hymenoptera Linnaeus, 1758
Suborders
Apocrita Symphyta

Hymenoptera is one of the largest orders of insects, comprising the sawflies, wasps, bees, and ants. The name refers to the heavy wings of the insects, and is derived from the Ancient Greek ὑμήν (humen): membrane and πτερόν (pteron): wing. The hindwings are connected to the forewings by a series of hooks called hamuli.

Females typically have a special ovipositor for inserting eggs into hosts or otherwise inaccessible places. The ovipositor is often modified into a stinger. The young develop through complete metamorphosis — that is, they have a worm-like larval stage and an inactive pupal stage before they mature (See holometabolism).

Contents 1 Evolution 2 Anatomy 3 Sex determination 4 Diet 5 Classification 5.1 Symphyta 5.2 Apocrita 6 See also 7 References 8 External links

Evolution

Hymenoptera originated in the Triassic, the oldest fossils belonging to the family Xyelidae. Social hymenopterans appeared during the Cretaceous.^[1] The evolution of this group has been intensively studied by A. Rasnitsyn, M. S. Engel, G. Dlussky, and others.

Anatomy

Hymenoptera are medium to large insects, usually with two pairs of wings. Their mouthparts are created for chewing, with well-developed mandibles. Many species have further developed the mouthparts into a lengthy proboscis, with which they can drink liquids, such as nectar. They have large compound eyes, and typically three ocelli.

The forward margin of the hindwing bears a number of hooked bristles, or "hamuli", which lock onto the forewing, keeping them held together. The smaller species may have only two or three hamuli on each side, but the largest wasps may have a considerable number, keeping the wings gripped together especially tightly. Hymenopteran wings have relatively few veins compared with many other insects, especially in the smaller species.

In the more primitive hymenoptera, the ovipositor is bladelike, and has evolved for slicing plant tissues. In the majority, however, it is modified for piercing, and, in some cases, is several times the length of the body. In some species, the ovipositor has become modified as a stinger, and the eggs are laid from the base of the structure, rather than from the tip, which is used only to inject venom. The stinger is typically used to immobilise prey, but in some wasps and bees may be used in defence.^[2]

The larvae of the more primitive hymenoptera resemble caterpillars in appearance, and like them, typically feed on leaves. They have large chewing mandibles, three thoracic limbs, and, in most cases, a number of abdominal prolegs. Unlike caterpillars, however, the prolegs have no grasping spines, and the antennae are reduced to mere stubs.

The larvae of other hymenoptera, however, more closely resemble maggots, and are adapted to life in a protected environment. This may be the body of a host organism, or a cell in a nest, where the adults will care for the larva. Such larvae have soft bodies with no limbs. They are also unable to defecate until they reach adulthood, presumably to avoid contaminating their environment, having an incomplete digestive tract.^[2]

Sex determination

Main article: Haplodiploid sex-determination system

Among the hymenopterans, sex is determined by the number of chromosomes an individual possesses. Fertilized eggs get two sets of chromosomes (one from each parent's respective gametes), and so develop into diploid females, while unfertilized eggs only contain one set (from the mother), and so develop into haploid males; the act of fertilization is under the voluntary control of the egg-laying female.^[2] This phenomenon is called haplodiploidy.

Note, however, that the actual genetic mechanisms of haplodiploid sex determination may be more complex than simple chromosome number. In many Hymenoptera, sex is actually determined by a single gene locus with many alleles. In these species, haploids are male and diploids heterozygous at the sex locus are female, but occasionally a diploid will be homozygous at the sex locus and develop as a male instead. This is especially likely to occur in an individual whose parents were siblings or other close relatives. Diploid males are known to be produced by inbreeding in many ant, bee and wasp species.

One consequence of haplodiploidy is that females on average actually have more genes in common with their sisters than they do with their own daughters. Because of this, cooperation among kindred females may be unusually advantageous, and has been hypothesized to contribute to the multiple origins of eusociality within this order.^[2]

Diet

Different species of hymenoptera show a wide range of feeding habits. The most primitive forms are typically herbivorous, feeding on leaves or pine needles. Stinging wasps are predators, and will provision their larvae with immobilised prey, while bees feed on nectar and pollen.

A number of species are parasitoid as larvae. The adults inject the eggs into a paralysed host, which they begin to consume after hatching. Some species are even hyperparasitoid, with the host itself being another parasitoid insect. Habits intermediate between those of the herbivorous and parasitoid forms are shown in some hymenopterans, which inhabit the galls or nests of other insects, stealing their food, and eventually killing and eating the occupant.^[2]

Classification

Giant Honey Bee Apis dorsata on Tribulus terrestris in Hyderabad, India

Symphyta

The suborder Symphyta includes the sawflies, horntails, and parasitic wood wasps. The group may be paraphyletic, as it has been suggested that the family Orussidae may be the group from which the Apocrita arose. They have an unconstricted junction between the thorax and abdomen, and the larvae of free-living forms are herbivorous, have legs, prolegs (on every segment, unlike Lepidoptera (butterflies and moths)), and ocelli.

Apocrita

The wasps, bees, and ants together make up the suborder Apocrita, characterized by a constriction between the first and second abdominal segments called a wasp-waist (petiole), also involving the fusion of the first abdominal segment to the thorax. Also, the larvae of all Apocrita do not have legs, prolegs, or ocelli.

See also

• List of bees, wasps and ants of Great Britain

References

1. ^ Hoell, H.V., Doyen, J.T. & Purcell, A.H. (1998). Introduction to Insect Biology and Diversity, 2nd ed.. Oxford University Press. p. 320. ISBN 0-19-510033-6. 
2. ^ ^{a b c d e} Hoell, H.V., Doyen, J.T. & Purcell, A.H. (1998). Introduction to Insect Biology and Diversity, 2nd ed.. Oxford University Press. pp. 570-579. ISBN 0-19-510033-6. 

• Grimaldi, D. and Engel, M.S. (2005). Evolution of the Insects. Cambridge University Press. ISBN 0-521-82149-5. 
• Rasnitsyn, A.P. and Quicke, D.L.J. (2002). History of Insects. Kluwer Academic Publishers. pp. 242–254. ISBN 1-4020-0026-X. 

External links

Wikimedia Commons has media related to: Hymenoptera

General

• Hymenoptera ForumGerman and International
• Hymenoptera Information System (German)
• Hymenoptera of North America - large format reference photographs, descriptions, taxonomy
• International Society of Hymenopterists
• Bees, Wasps and Ants Recording Society (UK)
• Ants Photo Gallery (RU)
• Fossil insects in Russia
• International Palaeoentomological Society
• Sphecos Forum for Aculeate Hymenopterra
• Hymenoptera images on MorphBank, a biological image database
• Order Hymenoptera Insect Life Forms

Systematics

• Hymenopteran Systematics
• Hymenoptera Online 1000+ images

Regional Lists

• Insetos do Brasil
• New Zealand Hymenoptera
• Waspweb Afrotropical Hymenoptera Excellent images

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