This highly specialised order was undoubtedly derived from free-living psocopteroid ancestors. It is divided into four very distinct suborders, the Amblycera and Ischnocera (chewing or biting lice, previously grouped together as the Mallophaga), Rhyncophthirina (elephant lice, also previously included in Mallophaga by some authors) and Anoplura (sucking lice). Over 3000 species are known.
There is a great diversity in size and body form. The adults range in length from less than 0.5 to 10 mm (males are usually smaller than females). They are highly modified for their parasitic existence, the most characteristic features being flattening of the body, complete aptery, and adaptations of tarsi for clinging to the feathers or hair of the host. Most species are well sclerotised, many are deeply pigmented, and some have a characteristic pattern. In some groups the body is covered with setae, but in others it is relatively bare.
The Rhyncophthirina are an anomalous group, which includes only the genus
parasitising African and Asian elephants and the African wart-hog.
General literature on the other suborders includes Hopkins and Clay (1952), Rothschild and Clay (1952) and Blagoveschenskii (1959) on Amblycera and Ischnocera, Hopkins (1949) on Amblycera, Ischnocera and Anoplura of mammals, and Ferris (1951), Kim and Ludwig (1978a) and Kim
. (1986) on Anoplura.
Apterous, dorsoventrally flattened, exopterygote Neoptera, with mouthparts mandibulate or piercing and sucking. Ectoparasitic on birds and mammals; entire life spent on hosts.