Horsehair Harry—Part 1

I recently met Harry the horsehair worm, the morning after a hot tub. I had never known such a creature existed, until I saw him squirming about at the bottom of the tub, as I began to drain it. I took a photo of him—later to investigate and discover what he was. Here’s some of what I found.

   

A horsehair worm is related to the nematode—a type of parasitic worm. It is extremely thin (about 1/16 inch) and several inches long… up to as much as a foot long. They writhe about, twisting themselves into a tangled blob that looks like a knotted cord. In fact, a common name for them is Gordian worm. An ancient myth has the worm spontaneously come alive from a horse’s tail hair—hence the name. In the fall they are usually found in pools of water (say, a horse drinking trough, in the old days), where they hunker down over the winter.

In the spring the horsehair worms get nasty. I last wrote about how we humans sometimes tend to romance nature. Here’s an example where nature gets pretty violent and ugly.

A group of worms will coil and knot themselves into orgiastic clumps, wherein the females become inseminated. Each mom then lays about  a million eggs that soon hatch and yield larvae—100 of them lined up end-to-end would hardly extend an inch. Biologists are not sure how, but the surviving larvae soon find their way into the gut of an insect—such as a cricket or a katydid, where they begin their odious parasitic life.

They first chew their way through the insect’s stomach wall and take up residence for a few weeks to a few months in the insect’s body cavity. The larvae have no food processing system—no stomach, no intestine, no anus. They have no circulatory or respiratory system either. They simply soak up nutrients from the interior of their hosts—absorbing food through their skin as they slowly destroy the host.

The larva molts several times and eventually grows into an adult worm—tightly coiled inside the insect’s body. It exudes a chemical that goes to the cricket’s brain—causing it to seek water and then drown itself, whereupon the worm breaks out and goes its way, leaving behind a hollowed-out, dead cricket.

It is now called a free-living worm, because it no longer lives the life of a parasite—when it was fully dependent for its existence on a host. Each mature worm lives through the winter (free at last!), never eating or excreting, just living on stored fat.

More on Harry next time…