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). Each female produces many thousands of triungulin larvae that escape from its body and out of the host into the soil and vegetation. These actively search out new hosts. Template:Userboxtop Template:Clade Suggested phylogenetic position of the Strepsiptera. Template:Userboxbottom Strepsiptera find and enter their insect hosts as planidium larvae. They undergo hypermetamorphosis and become a less mobile legless 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 William Kirby in 1813, is named for the hind wings (strepsi=twisted + ptera=wing), which are held at a twisted angle when at rest. The forewings are reduced to halteres.

Strepsiptera are an enigma to taxonomists. Originally it was believed they were the sister group to the beetle families Meloidae and Ripiphoridae, which have similar parasitic development and forewing reduction; more recent theories say they are the sister group to the beetles; even more recently, molecular genetic analyses have suggested that they are the sister group to the flies, which have hindwings modified into halteres. The earliest strepsipteran is the highly primitive Cretostylops engeli discovered in middle Cretaceous amber from Myanmar.

Families

Males of the family Mengeidae have 5-segmented tarsi with claws, the antennae are 6-7 segmented, the third and fourth segments have long lateral processes. Stylopidae have 4 segmented tarsi and 4-6 segmented antennae with the third segment having a lateral process. The Elenchidae have 2-segmented tarsi and 4 segmented antennae with the third segment having a lateral process. The Halictophagidae have 3-segmented tarsi and 7-segmented antennae with lateral processes from the the third and fourth segments. The Stylopidae mostly parasitize wasps and bees, the Elenchidae are known to parasitize Fulguroidea while the Halictophagidae are found on leafhoppers, treehoppers as well as mole cricket hosts.

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
• Survey of Modern Counterparts of Schizochroal Trilobite Eyes: Structural and Functional Similarities and Differences