Ensign Wasp or Hatchet Wasp

Description:

When I spotted this insect on the wall, it was vigorously shaking its hind legs, tail and antennae. It flew away after few minutes. The Evaniidae, also known as the Ensign Wasps or Hatchet Wasps, are a family of parasitic wasps. The larvae of these solitary wasps feed on cockroaches, and develop inside the egg-cases (oothecae) of their hosts.

Habitat:

Indoors. Wall. Friend's place.

Notes:

Ensign wasp larvae are predatory on the eggs of cockroaches. Host specificity and coevolution with roach lineages seem to have played a significant factor in the evolution of some ensign wasp lineages. Others are less discriminating in their host choice, and will attack almost any ootheca of a particular size. The female wasp lays an egg inside the roach ootheca (egg case), and the wasp larva hatches quickly and consumes the roach eggs. Technically, they are thus predators, rather than parasites or parasitoids as other parasitic wasps. A single egg is laid per ootheca, into a host egg in some Evaniidae, and between the eggs in others. Some are able to oviposit even when the female cockroach still carries the fresh ootheca around, while other ensign wasps will only attack oothecae that are completed and have been dropped by the mother roach. The wasps seem to be able to determine if an ootheca is already used to host a larva, and refrain from depositing eggs in such cases; alternatively, the larvae might be cannibalic, with the first to hatch in an ootheca eating any wasp eggs subsequently deposited.