Horsehair worms are white when they first emerge from the host's body but turn yellowish-tan to brownish-black after a short time. Insects infected with horsehair worms die as a result of the parasite. At the water, the horsehair worm emerges from the insect's body and swims away, an essential step in the life cycle of this internal parasite.

Parasitized crickets are thirsty and go to water to drink. This internal parasite of insects does not harm humans, animals, or plants. Amazingly, the entire horsehair worm grew and developed as a parasite inside the body cavity of crickets and other large insects such as grasshoppers, katydids, beetles, and cockroaches. Horsehair worms are very long (4 to 14 inches) and very narrow in diameter (1/25 to 1/16 inch wide). They may also be found on damp garden soil or vegetable plants after rain. The horsehair worms are interesting threadlike roundworms that resemble the 'hair of a horse's tail or mane.' These long, active worms may be observed in streams and ponds during late summer or fall but are more commonly noticed in domestic water containers such as bird baths, swimming pools, water troughs, pet dishes, sinks, bathtubs, and toilets. They are harmless to plants, people, and pets.Horsehair worms are mildly beneficial because a small percentage of crickets, grasshoppers, and other insects are infected and killed.Horsehair worms are also called Gordian worms because they resemble the 'Gordian Knot' of ancient Greek legend.

Long and slender parasitic roundworms of crickets and other large insects are occasionally present in pet dishes and other water containers.

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