Like other insects of the suborder Anoplura, adult head lice are small (2.5–3 mm long), dorso-ventrally flattened (see anatomical terms of location), and entirely wingless.[8] The thoracic segments are fused, but otherwise distinct from the head and abdomen, the latter being composed of seven visible segments.[9] Head lice are grey in general, but their precise color varies according to the environment in which they were raised.[9] After feeding, consumed blood causes the louse body to take on a reddish color.[9]
Head[edit]