Leptinus

Leptinus is a genus of beetle belonging to the family Leptinidae. This small family contains only a few species, all of which are ectoparasites. The most well-known species is Leptinus testaceus, commonly known as the beetle louse or parasitic beetle.

Leptinus testaceus is found in the Northern Hemisphere and is typically associated with nests of small mammals, particularly rodents such as mice and voles, as well as squirrels and bats. The adult beetles are small, flattened, and wingless, with a color that can range from pale yellow to reddish-brown. Their morphology is adapted for living in the fur of their hosts.

The life cycle of Leptinus testaceus is closely tied to its host. The adults feed on the blood and skin debris of the host animal. The larvae, which are also parasitic, may develop within the nest material or directly on the host. Reproduction and development are thought to be synchronized with the host's breeding cycle.

While considered parasitic, Leptinus species are not generally known to cause significant harm or transmit diseases to their hosts. Their presence is usually detected when the host animal is captured or its nest is disturbed. The adult beetles can survive for a period without a host, but they require one for successful reproduction. The family Leptinidae is considered a part of the superfamily Staphylinoidea.