The crab louse does not move much. When it has chosen its sucking place, it keeps the mouth inside the skin – also in the periods where it does not suck blood. Crab lice suck blood almost all the time. That is probably why they do not tolerate being away from their host for long periods of time. A single day without access to blood will cause them to die of hunger.
Crab louse bites and their symptoms are similar to those from the head louse. However, crab louse bites are characterized by blue-colored spots, which may appear where the lice bite. The spots, which are deep in the skin, appear a few hours after the bites. They may be 0.2 to 3 mm in diameter and will stay on the skin for a long time.