Grasshoppers become infected when they incidentally consume the eggs as they feed. During this time they lay tiny golden-brown eggs which they attach to plants. The adult nematodes are sometimes seen as they crawl on plants, usually following rainy periods in late spring. The head area of females is reddish-brown. The overall body color is very pale brown. It is extremely large, 5 to 20 cm, far larger than the nearly microscopic entomopathogenic nematodes often used to control various soil insect pests (see fact sheet 5.573, Insect Parasitic Nematodes). ( Photo courtesy of John Capinera.)Ī roundworm of the phylum Nematoda, Mermis nigrescens, develops as an internal parasite of grasshoppers (and perhaps earwigs). The Grasshopper Nematode ( Mermis nigrescens)įigure 1.

Both are harmless to humans but may attract attention and cause concern. Two unusual, very long ‘worms’ that are occasionally encountered are horsehair worms and the nematode parasite of grasshoppers, Mermis nigrescens. The common name ‘horsehair worm’ is derived from its occasional occurrence in livestock water troughs.With very few exceptions, horsehair worms will only be found in water.Moist conditions are favorable to the development of Mermis nigrescens and highest populations develop in relatively wet, grassy areas.Horsehair worms and the grasshopper nematode parasite, Mermis nigrescens, are both harmless to humans.

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