People once thought the worms were horsehairs come alive. Sometimes horsehair worms form groups of a couple dozen, wrapped together in an intricate tangle on the bottom of a spring or pond. Sometimes they are free swimming near the surface thrashing in slow motion like the one Josh snagged. On cold fall mornings they may be spotted on leaves of ragweed, covered in dew. Closer to home, they might create an early morning surprise in Fido's water dish or your toilet.
Horsehair worms are harmless to people, pets, and plants.
They start life as a larval parasite in a cockroach, beetle, cricket or grasshopper. Some may also infect snails and slugs. The worms we see in water are adults lucky enough to have made their way from their host to water. Those that can't reach water, like those living in grasshoppers perched on the ragweed on a cold September night, die quickly of dehydration. After leaving the host, the adults are no longer parasites.