Louse

Louse is a name applied to several different invertebrates that are either external parasite (harmful to the host) or commensals (not harmful). Included are certain crustaceans, such as the parasitic fish louse. Argulus Most commonly, however, the name refers to two groups of flattened, wingless insects living or warm-blooded animals. They are usually regarded as separate ofders; Mallophaga, or chewing lice, and Anophlura, or sucking lice.

Chewing lice are found on mammals but mostly commonly rodents. The crab louse and the head and body louse are sucking lice and the only lice that parasitize humans. Both lice glue their eggs or nits, to hair, but body the body louse may also fasten its eggs to clothing. The immature lice look like tiny adults.

In addition to the uncomfortable itching caused by its bites, the body louse may transmit the pathogens that cause typhus, replacing fever, or trench fever. The spread of these diseases, and of lice themselves, is closely associated with crowded, unsanitary conditions.


A body louse is a small, wingless insect that lives on humans, sucking its host’s blood. A louse egg, or nit is attached to the host hair.