Head Lice: The Parasitic Head Louse

Head louse is a small parasite, with the scientific name of Pediculus humanus capitisI, commonly found in hair of the head of humans and some other animals. It is specially adapted to living in hair on human head and neck. Head louse is different from pubic louse (living in pubic hair) and body louse (living in other body parts except head and pubic regions).

Body Structure

In its body structure, an adult head louse closely resembles a tiny ant. Like other arthropod animals (insects, crabs etc.) its body consists of a head, a thorax, and abdomen. It is tan to grayish white in color and has six legs.

Life of a Head Louse

Female head lice lay eggs, called nits, in the hair about a couple of centimeters above the scalp. The eggs are light in color, usually white or grayish white, and hatch in seven to nine days. Some eggs that dry out and die appear darker in shade. Once the female starts laying eggs, it continually lays three to seven eggs daily for about a month.

Three stages come in the life of a head louse: nit, nymph, and adult. Nits are firmly sticking to the hair shaft and are not seen easily. Nymph, or the baby louse that hatches from the nit, is identical to the adult form of the louse except that it is tiny in size. It grows to become an adult louse in a week.

The nymph feeds on human blood sucked from the skin of the scalp. Female lice are usually larger than males. All head lice are dependent on blood as food. If they fall off their host onto dead surrounding (not on another person), they die in a few days. Also, they would lay eggs on materials resembling the texture of human hair, i.e. synthetic hair of toy animals etc.

Contagious Mode of Living

Head louse is a highly contagious parasite. It rapidly spreads from one host to another especially in ideal situations like group settings in schools, child-care centers, sports etc. Head lice are wingless and cannot fly or jump from one person to another but they have an exceptional natural adaptation of crawling and clinging to hair and similar structures. Head to head contact is their main source of spreading.

But they also spread through sharing of household items like combs, hats, clothing etc. People who have close physical contact and generous sharing of such items are more apt to catching head lice, especially children and teenagers. However, pets do not catch and pass them on to humans.