DDT is a highly effective lousicide when used to control the body louse, Pediculus humanus corporis, the head louse, P. humanus humanus, and the crab louse, Phthirus pubis. DDT applied as a powder in any one of a number of diluents will provide almost complete protection from body lice for 3 weeks and effective control for a longer period and. is also effective in controlling head and crab lice. DDT impregnated clothing kills lice even after several launderings. Various types of liquid prepns. of DDT, including solns. and emulsions, are particularly effective against head and crab lice.