Horsehair Worm

Nematomorpha, commonly called horsehair worms or Gordian worms, is a phylum of parasitoid animals similar to but distinct from nematode worms. Most species range from 5 to 10 centimeters long, reaching up to 2 meters in extreme cases, and 1 to 3 millimeters in diameter; adults are free-living and found in damp places such as watering troughs, streams and puddles, while the larvae are parasitic on arthropods such as beetles, cockroaches, mantises and crustaceans. About 351 freshwater species are known, with a conservative estimate suggesting as many as 2,000 may exist worldwide. Their common name Gordian worm refers to the legendary Gordian knot, since the worms often coil themselves into tight, knot-like balls.