The Amazing Ichneumon

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Published on: May. 2, 2002

Last revision: Nov. 12, 2010

female. It alone is more than 3 inches long. These long ovipositors appear frightening, but megarhyssas do not sting.

Some ichneumon adults drink flower nectar and/or water, but most do not "eat" in the traditional sense. Some researchers suspect that many species do not take nourishment of any kind during the adult life cycle. All larval ichneumons consume other insects.

Ichneumon wasps range throughout the world, except the plains and deserts. They live all across the United States, except in the lower Southwest. Ichneumon wasps are found throughout Missouri. Though common, they are seldom seen or recognized because they usually feed, breed and lay eggs in places seldom visited or noticed by people.

Depending on the species, ichneumons prefer mixed forests with decaying logs, dead or dying broad-leafed trees, forest canopies and shrubby fields. They also live in meadows with a forest edge. They usually prefer damp habitats.

One species of ichneumon spends most of its life on and in the water. This special wasp is a parasite of the caddis fly larva, which matures underwater. The female ichneumon must dive to the underwater burrow of the caddis fly to deposit its eggs into the eggs of this species.

The ichneumon life cycle begins in the spring, when mature adults emerge and begin looking for mates. Ichneumon wasp courtship is simple and unpretentious. The female produces a strong sex pheromone capable of attracting males from long distances. These pheromones are similar to a strong perfume, but can only be detected by males of the species. Mating has seldom been observed in the wild, but scientists who study the ichneumon believe it lasts 10-20 seconds.

The most fascinating element of the ichneumon life cycle in the megarhyssa is its method of egg laying. After mating, the megarhyssa looks for the perfect site to lay its eggs, usually a dead elm tree that has been attacked by pigeon horntail flies. Apparently, the female selects the right tree by pressing its long antennae against the bark to detect vibrations of the horntail larvae deep inside the wood.

Finding the right tree, the female crouches on the tree and raises its hind legs as high as possible to guide the ovipositor straight into the wood. When in proper alignment for probing, the ovipositor is positioned more or less between the forelegs. The megarhyssa is able to retract some of its ovipositor in a loop

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