An e-mailer recently described to me an odd encounter she had with wildlife. She killed a cockroach by stepping on it. Before she could dispose of the dead cockroach, a narrow, worm-like organism that was several inches long crawled out of the cockroach and began weaving its body like a snake on the her floor. She had killed a cockroach that contained a parasitic horsehair worm. Not surprisingly, I guess, there are already several YouTube videos posted by others who have made similar observations. I don’t recommend viewing while eating. Other persons have recently reported seeing horsehair worms in lakes or wet ditches.
Also known as Gordian worms or hairworms, the organisms are a type of long worm that is related to nematodes. The name “horsehair worm” originated with the old superstition that the worms resulted from horse hairs that came to life when they fell into water. They do look like living hairs and, lacking heads and mouths, it’s easy to see why people have been confused about them.
The adult worms do not feed and can be found in running or standing water or on damp soil. Their eggs are laid in water or on damp soil. The larval forms can enter a variety of arthropod hosts, including beetles, cockroaches, crickets, grasshoppers, centipedes and millipedes. They are either ingested or can penetrate the host’s body. When full grown they exit the host when it is near water--or prematurely, when the host is stepped on by a human.
Although not very lovable creatures, horsehair worms do not injure humans or plants. They may be considered beneficial in helping to control populations of their host species. To me, they are just another of those surprises that nature throws at us to keep us from getting too complacent in our knowledge of the natural world.