Definition
A 'head louse' (Pediculus humanus capitis) is a wingless, parasitic insect that lives on the human scalp and feeds on blood. They are small, grayish-white, and lay their eggs (nits) on hair shafts. Think of them as tiny squatters on your head. They cause itching and are commonly spread through direct head-to-head contact, especially among children. While annoying, they don't usually transmit diseases.