There are two species of lice that infest humans: pubic lice, Pthirus pubis, and human head and body lice, Pediculus humanus.

Their study, Maintenance of the Crab Louse, Pthirus pubis, in the Laboratory and Behavioural Studies Using Volunteers, tells how they coated groups of pubic lice with powders that glow different colours under ultraviolet light.

SYMPTOMS: Often, no symptoms; sometimes abdominal pain and swelling; nausea TREATMENT: Treat with niclosamide (ni-KLOH-sa-mide), a worm-killing chemical CRAB LOUSE SCIENTIFIC NAME: Pthirus pubis (THY-ruhs PYOO-bis) CLASSIFICATION: Insect HABITAT: Pubic region; occasionally on facial or armpit hair HOW IT GETS THERE: Sexual contact or other close human contact; can be transmitted from toilet seat, towels, or other contaminated objects ACTUAL SIZE: 3 mm (about 0.