A female adult head louse clings to a hair plucked from a human scalp. The brown line visible inside the insect, on the left side of its body, is its last blood meal. Lice typically eat a few times a day.

A female adult head louse clings to a hair plucked from a human scalp. The brown line visible inside the insect, on the left side of its body, is its last blood meal. Lice typically eat a few times a day.