Phthiraptera are divided into the chewing lice (Mallophaga) and sucking lice (Anoplura).
These insects are wingless parasites that live on most birds and mammals. The chewing lice feed on bits of hair, feathers or skin of the host. The sucking lice feed mainly on blood. Lice deposit their eggs on the hair or feathers of the host. These insects are irritating pests that can be carriers of disease. Only the sucking lice contain members that attack humans. Phthiraptera undergo simple metamorphosis.
Suborder Mallophaga (chewing lice)
The chewing lice are sometimes consisted to be two suborders, the Amblycera and Ischnocera. They are small, flat, wingless, parasitic insects with mouth parts formed for chewing. Legs and antennae are short. Immature stages resemble the adults except for size. These insects feed upon feathers of birds or on hair and skin scales of other animals. They are important pests of domestic fowl and animals, but they do not live on man. About 1/6 to 3/16 inch long when mature. The chicken head louse, Cuclotogaster heterographus (Nitzsh) (Phthiraptera; Ischnocera: Philopteridae) is an example.
Suborder Anoplura (sucking lice)
Anoplura are small, flat, wingless, parasitic insects with mouthparts formed for piercing and sucking. Legs and antennae are short. Immature stages resemble the adults. These insects are found commonly on domestic animals, but not on birds. The human louse belongs to this suborder. They feed by sucking blood and are important pests of domestic animals and man. The human body louse has been responsible for millions of human deaths through the centuries. They spread the organism causing epidemic typhus from one person to another. The hog louse, Haematopinus suis (Linnaeus) (Phthiraptera; Anoplura: Haematopinidae) is an example.