Insects that can infest the skin and hair. Lice occur frequently throughout the world, and are particularly troublesome under conditions of poor hygiene. They regularly occur in schoolchildren in Western Europe, are resistant to low temperatures, but die quickly at temperatures above 50°C. Lice live for about a month, during which they produce 100-150 nits. When they bite, saliva enters the wound, causing itchy lumps. The body louse {Pcdiculus humanus corporis) closely resembles the head louse, lives in clothing fibres, and can lay about 300 eggs in its lifetime. It is no longer prevalent in Britain. The crab louse or pubic louse (Phthirus pubis) lives principally in the pubic-hair, but can also be found in armpit hair, eyebrows and eyelashes. It has a lifespan of roughly one month, and lays 20-50 eggs. Lice are dependent on the host, and die within a few days if they lose contact. An infested person rarely carries more than 20 lice. The host gradually becomes accustomed to them, and is hardly troubled by them. Lice can transmit diseases such as typhoid and trench fever.