Articles

Ichneumon Wasp

by Mark Stewart

The female ichneumon wasp wants only the best dietary delicacies for her future offspring. In this case, it is the tender larvae of the giant wood wasp known as sirex. The problem is that sirex, unlike many self-respecting insect larvae, refuses to be caught out in the open and spends its entire existence buried in the depths of tree trunks. But the female ichneumon wasp is not in the least bit daunted by such subsurface subterfuge (an evasive trick or tactic). Using her antennae, she can literally "smell out" an unsuspecting sirex beneath the surface of a tree trunk.

But locating a potential victim is only half the reproductive battle. Somehow the female ichneumon wasp has to deposit an egg on a creature separated from her by an inch or more of solid wood. Again she comes admirably equipped for the
task. The female ichneumon possesses a needlelike ovipositor (egg depositor) longer than her head and body combined. Whenever she locates a sirex larva, she unsheathes her stiletto-like appendage and jabs it into the appropriate spot on the surface of the tree. Invariably she is right on target and leaves an egg attached to the body of the unsuspecting sirex.

But the ichneumon wasp's remarkable boring qualities don't end there. In many cases she has to know whether the invisible sirex is right for her blood-sucking larvae. For instance, a particular sirex already victimized by another wasp would be unable to play host to two or more ichneumon offspring. Apparently her keen sense of smell is also instrumental in making this bore/no-bore distinction.

Her young offspring have their own boring tasks to perform as well. When they
emerge from the pupal stage, they must chew their way out of their woody chambers to daylight. Somehow the young ichneumons have to know which way is up or the result could be entombing themselves deep within the trunk of the tree.

Now some people might say that such knowledge comes by instinct. Instinct is an umbrella word, beneath which naturalists seek shelter whenever questions become too pressing and they have not the faintest idea of the true answer. And that is the true answer in this case (that of the young ichneumon wasp): nobody knows. That is, almost nobody, if we are willing to give any credit for the ichneumon wasp's behavior to the work of a higher intelligence.

Why, for instance, should she pick on sirex when other visible prey would be much more accessible? Once she deposits her egg, she has no further "knowledge" of what its chances of future survival will be. So clearly trial and error is out of the question. Somehow the female wasp also knows that boring holes in tree trunks is the thing to do, but she obviously has no knowledge of why she does it. And looking at her ovipositor one would be hard pressed to deny that such a fearsome-looking tool was intentionally designed for drilling purposes. Yet by whom or by what? Presumably one could answer that blind, undirected forces of natural selection was responsible. But a much more reasonable conclusion would seem to include the work of a highly intelligent creator.