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Page: Life Cycle
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Louse eggs on the hair very close to the scalp are the primary sign of an active infestation. A female can lay up to 50-150 eggs in its life, but it can lay up to 100 eggs in 30 days. She also glues her eggs, sometimes called "nits", which look like tiny white beads, to hair shafts very close to the scalp (usually about a centimeter or two [half an inch to three-quarters of an inch] from the scalp). Eggs are very small, about the size of a period "." (full stop) in normal printing. Eggs may appear white, yellowish, brownish or greyish, but are almost always lighter colored. An egg normally undergoes a 7-9 day incubation before hatching as a baby nymph. It can be passed to adult to child or child to adult
Classically, a louse egg does not become a "nit" until after it has completed its incubation stage, thus leaving a "nit." A "nit" is either the empty shell remaining after the nymph has departed or the dead egg that remains if incubation was not successful. Dead eggs will appear darker, or raisin-like, as they dry out. "Nits" of this sort are usually found over one centimeter (approximately one-half inch) or more away from the scalp and are not considered a sign of active infestation. Some people refer to lice eggs, live or dead, as "nits." In common usage, an egg that is still incubating may also be called a "nit."
Head lice have no wings and move primarily by crawling. They have no adaptations for jumping.
Whether a louse is male or female is not apparent until it is nearly mature. Fertilization of eggs takes place once the female is mature. The female can then lay 3-7 eggs each day for the next 28 to 30 days, her normal life span. Females may lay multiple eggs on one hair or lay an egg on a hair and then move on.
There are three main stages in the life of a head louse: the nit, the nymph, and the adult.
* Nit: Nits are head lice eggs. They are hard to see and are found firmly attached to the hair shaft. They are oval and usually yellow to white. Nits take about 1 week to hatch.
* Nymph: The nit hatches into a baby louse called a nymph. It looks like an adult head louse, but is smaller. Nymphs mature into adults about 7 days after hatching. To live, the nymph must feed on blood. It metamorphoses 3 times before it reaches the adult stage. Most head lice at this stage are almost transparent until they have eaten (sucked blood from a human skin). Then they can be seen more easily since it will be possible to see the tiny amount of red or brown blood in their stomach. To the unaided eye, it will appear like a small red dot usually about 0.5 mm or less in diameter. With a magnifying glass or microscope it is possible to see the head and legs, and since a louse is quite transparent at this stage, the digestive system, showing the blood that was ingested.
* Adult: To live, adult lice need to feed on blood. Females are usually larger than males, and can lay several nits in a day. If the louse falls off a person, it usually dies within 1-2 days[citation needed], although experiments have shown them to live longer. A female may continue to lay eggs on other materials similar to the texture of human hair such as stuffed animals with long strands of hair.
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Important notice:
The content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other
qualified health provider with any questions you may have regarding a medical condition.
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