Pubic lice. Coloured Scanning Electron Micrograph (SEM) of two pubic lice, Phthirus pubis, also known as crab lice, hanging from human hair. An adult louse and infant louse are seen. An infestation of P. pubis causes pediculosis, the symptoms of which are severe itching and a rash. The lice suck blood, feeding five times a day. They spread through sexual contact and through bedding and clothing. Each of the louse’s six legs terminates in a massive claw, which folds inward to meet a thumb-like projection on the opposite side. The louse climbs & swings through its habitat, locking into position when disturbed. Magnification: x20 at 6x7cm size.