Head lice are six-legged wingless insects measuring between 2-3 millimeters, about the size of a sesame seed. They can vary in color from grayish white to reddish brown and have the ability to adapt their color to their environment.
While they cannot jump or fly, head lice can crawl quickly along the hair shaft. As parasites, they depend on human blood for survival and must have a “blood meal” (at the scalp) every two to three hours to survive.
The female has a lifespan of up to 30 days, during which time she can produce between three and 10 eggs (nits) per day, attaching them to the hair shaft, generally close to the scalp where environments are the warmest.
Nits may look like dandruff but can vary in color from whitish to tan to even reddish brown, making them hard for an untrained eye to recognize and see. They are attached to the hair with a sticky glue-like protein substance which forms a bond that is difficult to break without specialized products and techniques.
Nits hatch between one and two weeks after they’re laid. Baby lice are known as nymphs, and they become adult lice between one and two weeks after hatching. Adult lice mature to about the size of a sesame seed.
Though very small, lice can be seen with the naked eye. Nymphs and nits are even smaller and it may require an expert to identify them with certainty.