What does a head lice infestation look like?

Head Lice. Adult lice on scalp. The most common spots to find adult lice are behind your ears and along the back of your neck. Lice are tiny, about the size of a strawberry seed, but they can be up to 1/8 inch (3 millimeters) in size. Lice eggs (nits) on hair shafts. Nits resemble tiny pussy willow buds. Nits can be mistaken for dandruff, but unlike dandruff, they can't be easily brushed out of hair.
See below. The most characteristic feature is the presence of "nits" (lice eggs) attached to the hair shafts. These are tiny specs that look like dandruff, but are glued on to the hair shaft and cannot be flicked off, although you can slide them off the hair shaft. In more severe cases, adult lice, which look like tiny 1mm - 2mm diameter crabs are visible.