Strepsiptera

Lore & Background

Adult male Strepsiptera have wings, legs, eyes, and antennae, but their mouthparts cannot be used for feeding. Their forewings are modified into small club-shaped halteres that sense gyroscopic information, while the hindwings are fan-shaped with reduced venation. Their eyes are unlike those of any other insect, consisting of only a few dozen 'eyelets' that each produce a complete image, giving the cluster eye a blackberry-like appearance. Females of the suborder Stylopidia, which includes 97% of all described species, are neotenic, lacking wings, legs, and eyes, and never leave their hosts; they have a well-sclerotised cephalothorax. Adult female mengenillids are wingless but free-living and somewhat mobile.

Reader's Guide

Strepsiptera are significant as obligate endoparasites that manipulate the behavior and reproduction of their hosts, including bees, wasps, ants, and grasshoppers. Their life cycle involves traumatic insemination, where the male ruptures the female's cuticle to deposit sperm, and haemocoelous viviparity, where larvae hatch inside the female and consume her from within. The order is not well known to non-specialists, but its evolutionary position has been debated; molecular studies suggest they are outside the clade Mecopterida, but no strong affinity with any extant group has been confirmed. Their fossil record begins in the mid-Cretaceous, though they are believed to have diverged from beetles 300–350 million years ago. The name Strepsiptera means 'twisted wing,' referring to the twisted angle of the hindwings at rest.

Did You Know?

• Male Strepsiptera have eyes resembling those of the trilobite group Phacopina, with each eyelet producing a complete image.
• Females of most species never leave their host and die inside it, while males are short-lived, typically surviving from a few hours to a few days.
• The larvae of Strepsiptera undergo hypermetamorphosis, transforming from highly mobile first-instar larvae into legless, immobile forms inside the host.
• In the family Myrmecolacidae, males parasitize ants while females parasitize grasshoppers and crickets (Orthoptera) or sometimes other insects.