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Mengenillidae
Mengeidae
Stylopidae
Bohartillidae
Corioxenidae
Halictophagidae
Callipharixenidae
Elenchidae
Myrmecolacidae
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Species in the nine families of this small (~600 species) order of insects are parasites in other insects; their hosts include bees, wasps, leafhoppers, silverfish, and cockroaches.
Male Strepsiptera have wings, legs, eyes, and antennae, and look like flies, though they generally have no useful mouthparts. Females, in all families except the Mengenillidae, never leave their host and are neotenic in form, lacking wings and legs. Males have a very short adult lifetime (usually less than five hours) and do not feed as adults. They search for and mate with a female (whose anterior region extrudes through the host's body). Sperm passes through an opening in the head of the female and from there directly into the body cavity (Haemocoel).
Male Strepsipteran eyes are unlike those of any other insect, resembling the schizochroal eyes found in the trilobite group known as Phacopida. Instead of compound eyes consisting of hundreds of ommatidia, each of which sees one pixel, the strepsipteran eyes consist of a few dozen lenses, each with its own individual retina.
The order, named by Kirby in 1813, is named for the hind wings (twisted wing), which are held at a twisted angle when at rest. The forewings are reduced to halteres.
Strepsiptera present an enigma to taxonomists. Some believe they are the sister group to the beetle families Meloidae and Rhipiphoridae, which have similar parasitic development and forewing reduction; some say they are the sister group to the beetles; some say they are the sister group to the flies, which have hindwing halteres.
