AY Honors/Insect/Strepsiptera

The Strepsiptera (occasionally known as twisted-winged parasites) are an order of insects with nine families making up about 610 species. They are parasitoids on 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).

Strepsiptera enter their insect hosts as larvae. They undergo hypermetamorphosis and become a less mobile larval form. In this stage they feed within the host's body cavity. The colour and shape of the host's abdomen may be changed and the host usually becomes sterile. The parasites then undergoes holometabolous metamorphosis to become adults. Adult males emerge out of the host body while females stay on inside.

Male Strepsiptera have eyes 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 are 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 hindwings modified into halteres. The earliest strepsipteran is the highly primitive Cretostylops engeli in middle Cretaceous amber from Myanmar.

References

• Grimaldi, D. and Engel, M.S. (2005). Evolution of the Insects. Cambridge University Press. ISBN 0-521-82149-5.

External links

• http://tolweb.org/tree?group=Strepsiptera
• http://www.strepsiptera.uni-rostock.de/
• Survey of Modern Counterparts of Schizochroal Trilobite Eyes: Structural and Functional Similarities and Differences