There are many types of lice such as, body, pubic and head lice. The head louse, or Pediculus humanus capitis, is a parasitic insect that can only be found on the head.
There are three stages of the lice life cycle: egg, nymph and adult.
Head lice have six claws designed for them to crawl from hair strand to hair strand. These claws allow them to move from head to head.
HEAD TO HEAD
A head-lice infestation occurs when a female adult louse moves to a new head and lays eggs. When those eggs hatch, the lice will most likely stay on that head throughout the entire lice life cycle. Unless the head is treated and all lice and eggs are killed, the lice infestation will continue for however long the lice can live.