Human head and body lice are ecological variants of the same species, capable of adapting to the different ecological conditions on the human scalp, torso or clothing. They are genetically intermixed and their behavioral ecology has been extensively studied as they are the vector for several important human diseases.
Both forms feed on blood. However, their ecology differs between body morphs. Head lice feed at regular intervals every few hours, whereas body lice feed only once or twice per day during periods of host inactivity.