Lice eggs are light yellow, oval, 0.9~1.0mm long, and have a cover at one end. When laying eggs, female lice use their tail ends to hold onto hair or clothing fibers and secrete glue to stick the eggs to prevent them from falling off. Both head lice and pubic lice lay their eggs on the hair, while body lice lay their eggs on the fibers of clothing.

Lice eggs hatch from the egg shell after 6 to 8 days of development and are called nymphs. The morphology of nymphs is basically similar to that of adults, except that they look slightly lighter in color and smaller in size. The nymphs can feed on blood as soon as they hatch, and it takes about 9 days to molt three times to become adults.

Lice (shi) belong to the class Insecta, order Anoplura, and family Pediculidae. It is a small wingless insect with a flat body dorsally and ventrally. It is a permanent external parasite. It is also a general name for a type of small, wingless parasitic insects, divided into two major groups: Amblycera and Ischnocera (also known as chewing lice or biting lice), which are parasitic on birds and mammals. ; Anoplura suborder, parasitizing only mammals.

There are three types of lice that parasitize the human body, namely Pediculus humanus corporis, Pediculus humanus capitis and Phthirus pubis. Body lice and head lice are varieties of human lice in the genus Pubic lice, while pubic lice are a separate genus Pubic lice. Among the three types, body lice are the most important. They are an important vector for the transmission of epidemic typhus and louse-borne relapsing fever, that is, trench fever.