Horsehair Worm (also known as Gordian Worm)
Scientific Name: Gordius types (Phylum Nematomorpha)
Order & Family: Order: Gordioidea, Family: Gordiidae
Size: Typically extremely long and thin; 4 to 14 inches (10-35 cm) or more in length, but only 1-3 mm in diameter.
Natural Habitat
Adults are free-living in freshwater environments like puddles, streams, troughs, and swimming pools. Larvae are internal parasites of terrestrial insects.
Diet & Feeding
Adults generally do not feed, relying on energy stores. Larvae are parasitic and absorb nutrients from the internal body fluids of hosts like crickets, grasshoppers, and cockroaches.
Behavior Patterns
Famous for their parasitic lifestyle where they manipulate the host's behavior, compelling the insect to seek water and drown itself so the adult worm can emerge to breed. They often writhe in knots, resembling the legendary Gordian Knot.
Risks & Benefits
Harmless to humans, pets, and plants; they cannot infect mammals. They are considered beneficial ecologically as they help control populations of pest insects like roaches, crickets, and grasshoppers.
Identified on: 2/19/2026