Horsehair worm
Scientific Name: Gordius robustus (and other species in the phylum Nematomorpha)
Order & Family: Gordioidea; Gordiidae
Size: Generally 4 inches to 14 inches (10 cm to 35 cm) long, but very thin (1-3 mm).
Natural Habitat
Freshwater environments like streams, ponds, puddles, or cisterns; larvae are internal parasites of insects.
Diet & Feeding
Larvae absorb nutrients from the body cavity of insect hosts (like crickets or beetles); adults do not feed.
Behavior Patterns
As larvae, they are endoparasites that can manipulate the behavior of their insect host to jump into water. They emerge from the host as adults to mate in aquatic environments.
Risks & Benefits
Harmless to humans, pets, and plants; they provide an ecosystem benefit by naturally controlling populations of crickets, cockroaches, and beetles.
Identified on: 2/14/2026