ichneumon fly (ĭknōˈmən) [key], common name for a family of insects, related to the wasps, whose larvae are parasitic on many other insects. Over 3,000 species of ichneumon flies, also known as ichneumon wasps, are found throughout the United States except in the Southwest. The female has an extremely long ovipositor capable of piercing through several inches of insect-infested tree trunk to the caterpillars and other larvae within. When the eggs hatch, the ichneumon larvae feed on the body of the host. One species parasitizes the aquatic larva of the caddisfly, and the female must dive to the underwater burrow of the host to deposit her eggs. Ichneumon flies are harmless to humans and trees, and in fact help to keep many insect pests under control. Other wasps, such as the braconid wasps, are also larval parasites of insect hosts. Ichneumon flies are classified in the phylum Arthropoda, class Insecta, order Hymenoptera, family Ichneumonidae.
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