Giant ichneumon megarhyssa-Aug 2017 DSC 2242

The female Giant Ichneumon wasp, Megarhyssa marurus, possesses an ovipositor several times her own length with which she drills into the side of diseased trees to lay an egg on the larva of another wasp, the pigeon horntail. The horntail prey larva is killed, and after hatching the ichneumon larva feeds upon it. The ovipositor is composed of a central delivery shaft through which the egg passes, and two outer sheaths that protect and stiffen the central “hypodermic needle”. At the beginning and end of the drilling process the last segments of the tail split apart and a flexible membrane is inflated between them, (the white moon-shaped structure in the photo), and in ways not clear, at least to me, this assists in the manipulation of the ovipositer as it enters and leaves the wood. Before the drilling begins the wasp walks methodically up and down the tree, “feeling” with her antenna to sense the presence of the host larva buried below the surface.