Strepsiptera (stylops)

All strepsiptera are parasitic, mainly on bees, but also on wasps and bugs. The sexual organs of insects parasitised do not develop, and the males look a little like the females of their species and vice versa. Some insects also behave more sluggishly. Strepsiptera do not normally kill their hosts.

The adult female looks like a soft and fleshy maggot, but as she passes her entire life inside her victim she is never seen unless removed. Normally all that is seen is the hardened tip of her head and thorax. She has no wings, limbs, eyes or antennae. A female can produce up to 70,000 eggs.

Males undergo pupation within the insect, then emerge fully into the open. Males are small, usually less than 4 mm long, and their body is dark brown or black. They have a large thorax for their size, branched antennae and protruding eyes. They have one pair of wings which fold fan-wise. In front of each wing there is a twisted, club-shaped appendage - perhaps the remnant of an ancestral wing or elytra (see the adult male above). These appendages act as balancers rather like the halteres in true flies. Males live for only a few hours as an adult.

The larva lives inside the body of the insect it parasitizes. On hatching from the egg the larva makes its way to the abdominal surface of its host. It has 6 legs at this time and a body shape like a woodlouse. The larva is taken to another host either by the bee returning to its nest, or by getting off at a flower and waiting for another insect to pass by.

Once it has found its host it buries itself in the abdomen, loses its legs, and absorbs food from the host's haemolymph. Only once it has pupated does it push its head between the segments of the insect abdomen.