Three Life Stages of Pubic Lice: Nit, Nymph, and Adult

Pubic lice, or "crabs" as they are commonly referred to, are parasitic insects which live on the pubic hairs of humans - including those of the groin, anus, face (beard, mustache, eye-lashes) abdomen, and underarms. Pubic lice feed exclusively on the blood of their hosts, resulting in irritation and itching around bites. Because a single louse feeds 4 to 5 times a day, an infestation can cause serious discomfort.

Life Cycle Basics

The female louse will mate soon after taking a blood meal. After gestating only 1 to 2 days, the female will lay her eggs - or nits - at the base of a hair, close to the skin. In a little over a week the eggs will hatch, allowing the emergence of an immature louse known as a nymph. After another 10 days, the nymphs will have matured into adult lice, capable and mating and producing more eggs.


Lice eggs, or nits, are found firmly attached at the base of a hair. They are usually yellow or white in color and are about the size of a 12 point font comma. Although they are very difficult to see, nits are often the easiest stage to identify due to their immobility. However, they can often be confused with dandruff or debris.


Nymphs emerge from their eggs after approximately 10 days of incubation. They are sexually immature and therefore cannot mate with other adults or nymphs. However, they do feed on blood and therefore cause the same itching and irritation as adult bites. Nymphs are essentially a smaller version of adults, making them very difficult to find. Their small size along with their mobility make them tricky to locate and are therefore rarely used in diagnosis.


Nymphs mature into adults after about 10 days. Adults are tan to grayish-white in color and are about 1-2 mm in size. They have six legs, including two prominent front legs which look much like the pincers of a crab - hence the nickname.

Prevention & Treatment

Pubic lice are most often spread during sexual contact. Be sure you know your sexual partner well and are aware of his/her sexual history. Limiting your number of sexual partners will greatly decrease your chances of contracting pubic lice. A person may not present symptoms for 2 to 6 weeks after coming into contact with an infested individual, making it possible for someone to spread pubic lice without knowing they have it themselves.

All life stages may be identified with a strong magnifying glass and removed with forceps.

Nits, nymphs and adults can also be removed by applying a water/rubbing alcohol/anti-lice shampoo mixture to hair and then brushing from base to tip with a metal comb. Although most lice and eggs can be removed this way, adults and nymphs can easily go unnoticed, making further treatment a necessity to completely clear an infestation. Washing any linens that may have come in contact with infected individuals is also recommended to clear an infestation. Bedding, clothing, and towels should be washed in water that is at least 50° Celsius (122° Fahrenheit) and dried in a hot dryer for at least 20 minutes.

Because lice cannot live more than a few hours detached from a human hair, any lice seen on furniture or linens are likely to be dead and no longer infective.


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