Insect order that comprises over 100,000 species, including the bees, wasps, and ants. Representatives may be social or solitary, free or parasitic.
They are insects with two pairs of wings, the forewings and hindwings being interlocked by means of hooklets. The wing venation is often reduced and the hindwings are usually smaller. The abdomen is usually constricted forming a ‘waist’. An ovipositor (egg-laying organ) is always present and modified for piercing, sawing or stinging. Metamorphosis is complete, and the larvae are usually without legs.
Hypermetamorphosis (in which the larva passes through several distinct forms) is not uncommon, especially in the parasitic species. Pupae are usually in a cocoon. with a great range of specialization of form. Parthenogenesis is frequent, in some cases giving rise only to males but in others producing females as well.
Suborder Symphyta consists of the more primitive hymenopterans. The waist is not present and the ovipositor is adapted for sawing or boring. Parasitism is rare. Most species have larvae associated with vegetation and three families contain members of importance to forestry and agriculture: the Siricidae (wood wasps and horn tails) have larvae that burrow into trees; the Diprionidae (conifer sawflies) cause defoliation of pine trees; and the Cephidae (stem sawflies), contain species that damage wheat crops.
Suborder Apocrita contains the majority of Hymenoptera with the typical ‘waisted’ appearance. There are a large number of parasitic families, all with the ovipositor adapted for piercing. Several families produce galls on plants. The Cynipidae, for instance, produce the familiar oak galls and also those on roses. Most are parasitic on other insect eggs, larvae, or pupae, and several are used for biological control of pests. The families are grouped in the superfamilies Trigonaloidea, Ichneumonoidea, including ichneumon flies, Evanioidea, Cynipoidea, including gall wasps, and Chalcidoidea. Most are small insects. The two superfamilies Proctotrupoidea and Bethyloidea also contain many species that are parasitic on other insects or form galls.
The other members of Apocrita have the ovipositor adapted for stinging, and are mainly colonial insects more generally recognized as bees, ants, and wasps. The superfamily Scolioidea contains primitive members of this group, sexual dimorphism is common and some species are parasites of bees and other insects.
The ants form superfamily Formicoidea of suborder Apocrita. They are generally treated as a single family, Formicidae. There are some 8,000 species. They are all social, with distinct castes.
The superfamily Pompiloidea contains solitary wasps, which usually build simple subterranean nests, and are parasitic on spiders. The paralysed spiders are stored in the nests for the young to feed on. The superfamily Vespoidea contains only one family, Vespidae, the true wasps. They may be either solitary or social.
Hymenoptera is in subclass Pterygota, class Insecta, phylum Arthropoda.
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