Pubic louse. Coloured scanning electron micrograph (SEM) of pubic louse (Phthirus pubis), also known as the crab louse, clinging to human hair. An infestation of P. pubis causes pediculosis, the symptoms of which are severe itching and a rash. The lice feed by sucking blood and are spread through sharing bedding and clothing, or by sexual contact. Each of the louse's six legs ends in a massive claw, which folds inward to meet a thumb- like projection on the opposite side. These claws allow the louse to climb and swing through its hairy habitat, locking into position when disturbed. Magnification: x60 when printed 10cm wide.