Insects

Phthirus pubis. Male pubic louse, ventral view (unstained, scanning power). Known as the "crab louse" or pubic louse, these lice usually live attached to hair in the pubic and perianal regions, but they also can be found on eyelashes, hair of the face, the axilla, and elsewhere; they are infrequently found on the scalp. These lice feed at the same body site for many days. Eggs of crab lice are smaller than those of body lice, and the mass of cement that attaches them to hairs is relatively larger. Although crab lice resemble body lice (Pediculus species) in general anatomy, they are rounded and almost circular in shape; in addition, the paired front legs are less well developed than the two pairs of hind legs. Females can be distinguished from males by examining the tip of the abdomen, which in the former shows the presence of claspers and gonopods while in males the penis (aedaegus) usually protrudes from the sexual opening.