Taxonomic placing: Insecta.
A group of insect orders with incomplete metamorphosis. The wings develop externally (thus also called Exopterygota), either on the later juvenile instars (nymphs) (e.g. Orthoptera, most Hemiptera) or during the so-called prepupal and pupal stages (e.g. Thysanoptera and the Coccoidea in the Hemiptera). The juvenile insects usually resemble the adults. The Hemimetabola comprises about 15 orders, including pests of agricultural importance in the Hemiptera, Orthoptera and Thysanoptera. Other Hemimetabola, which are of medical and veterinary importance, include the biting or bird lice, Mallophaga, the sucking lice, Siphunculata (Anoplura) and various blood-sucking Hemiptera.