Adult lice are about 2 to 3 millimeters long, about the size of a sesame seed. They’re tan or grayish-white. The color can be lighter or darker, depending on the shade of your hair. Adult lice have six legs with claws at the end that allow them to latch tightly to your hair. Typically, adult head lice live 30 days when stuck to your head. If they fall off, they die within 1 to 2 days.