Close-up picture of adult head lice, with a match head and a coin for size comparison. The larger female is on the right.
Picture of a lice comb in use. The small dark spots in the foam are lice.
Picture of lice nits attached to hair.
Magnified picture of an adult head louse. This louse is actually just under 1/8 inch or about 3 mm long, which is about the size of a sesame seed.
Source:
Center for Disease Control (CDC), Division of Parasitic Diseases (DPDx)
A female adult louse (magnified) that is about the size of a sesame seed (3-4 mm long or less than 1/8 inch). Although difficult to see, there are eggs (nits) located in its abdomen. Nits are often mistaken for bits of dandruff or droplets of hair spray. Eggs are attached to hair shafts with a cement-like substance that makes them difficult to remove. Nits are generally laid within 6 mm (1/4 inch) of the scalp, in order to remain warm.
Source:
Center for Disease Control (CDC), Division of Parasitic Diseases (DPDx)
Picture of adult head lice which is about the size of a sesame seed. Note the claw-like structures on the legs allowing lice to cling to hair shafts. Adult head lice, known scientifically as
Pediculus humanus capitis, tend to live within 1/4 inch of the human scalp for warmth, and lay their nits in the same area. Body lice are known as
Pediculus humanus humanus and are located around the torso.
Source:
Center for Disease Control (CDC), Division of Parasitic Diseases (DPDx)
There are three distinct phases in the life cycle of head lice: the egg, the nymph, and the adult form.
Nits: These lice eggs are tiny and hard to see. They may be overlooked as being hair spray beads or even dandruff flakes. The female adult louse cements these eggs to the base of the hair shaft within about 1/4 inch of the human scalp.
(1) These tiny, oval yellow to white eggs measure about 0.3 mm by 0.8 mm (less than 1/64 inch by 1/32 inch). Nits hatch in about a week, with a range of 6-9 days.
Nymphs: The hatched nit releases a nymph, which has a size similar to the head of a pin, but looks like an adult louse. The nymph's old shell remains attached to the hair shaft, becoming a more visible dull yellow color. Nymphs molt three times during the week after hatching
(3) &
(4), and reach the mature adult louse stage.
Adult lice: The tan to gray-white adult louse is about the size of a sesame seed and has 6 clawed legs
(5). If the infested person's hair is dark, the louse will appear darker as well. The larger adult females can lay up to 8 eggs daily. Adults can live as long as 30 days on a human head and require frequent meals of blood. Any of these human parasites which fall off the head (or are removed) will die within 24-48 hours without food.
Source:
Center for Disease Control (CDC), Division of Parasitic Diseases (DPDx)
