Horsehair Worm
Scientific Name: Gordius robustus (and related species in the phylum Nematomorpha)
Order & Family: Order: Gordioidea; Family: Gordiidae
Size: Commonly 4 inches to over 14 inches (10 to 35 cm) long, but extremely thin (usually 1 to 3 mm in diameter).
Natural Habitat
Typically found in freshwater environments such as streams, ponds, puddles, and drainage troughs, but often emerge from their insect hosts onto land.
Diet & Feeding
As larvae, they are internal parasites of insects like crickets, grasshoppers, and beetles, absorbing nutrients directly from the host's body. As adults, they do not eat.
Behavior Patterns
They exhibit a unique life cycle where the larva infects an insect and eventually manipulates the host's behavior to seek out water. Once the host is in water, the adult worm emerges to mate and lay eggs.
Risks & Benefits
They are harmless to humans, pets, and livestock. They are beneficial to the ecosystem by helping to control populations of certain insect pests.
Identified on: 12/31/2025