Horsehair Worm
Scientific Name: Nematomorpha
Order & Family: Phylum Nematomorpha, Order Gordioidea (for freshwater species)
Size: Typically 10-50 cm (4-20 inches) long, but can be much longer, and about 1-3 mm in diameter. Some species can reach up to 2 meters.
Natural Habitat
Adults are free-living in freshwater environments (puddles, ditches, ponds, streams, stock tanks, swimming pools) or sometimes damp terrestrial environments. Larvae are parasitic inside arthropods (crickets, grasshoppers, cockroaches, mantids, beetles, etc.).
Diet & Feeding
Adults do not feed. They live off nutrients accumulated during their parasitic larval stage. Larvae are endoparasites, absorbing nutrients directly from their host's body cavity.
Behavior Patterns
Adults are often found tangled together in masses, resembling a 'Gordian knot' (hence the family name Gordioidea). They use chemical cues to find suitable host arthropods while in their larval stage. When mature, the parasitic worm manipulates its host to seek water, where the adult worm emerges and reproduces. This host manipulation is a fascinating example of parasitic behavioral control.
Risks & Benefits
Generally harmless to humans and vertebrates, as they cannot parasitize them. They are not known to transmit diseases. Horsehair worms can be a natural control agent for some insect pests, such as grasshoppers and crickets, but their impact on pest populations is usually localized and not significant for widespread control.
Identified on: 9/24/2025