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Pubic Lice/Crab Lice

- Tiny, biting insects that resemble crabs -

Summary: Pubic lice, sometimes called "crabs" or crab lice, are tiny, blood-sucking insects that cause intensely itchy lesions when they bite. Pubic lice attach their eggs to the coarse hairs of the groin, armpits and sometimes eyebrows.

Jack DeAngelis, PhD
OSU Ext. Entomologist (ret.)

Identification of crab/pubic lice (Pthirus pubis)

Pubic (crab) lice are tiny (1-2 mm) blood sucking insects. The common name pubic louse ("louse" is the singular form of the word "lice") comes from where they are typically found -- in the pubic area of infested individuals but they may also be found in armpit, chest and eyelash hair.

The other common name crab louse comes from their overall shape as well as the two pairs of enlarged claws, features which resemble real crabs (see photo right). These modified claws are adapted for grasping coarse pubic hairs. This tiny insect has been a highly specialized "companion" of humans, and some of our primate cousins, since before recorded history.

other common name: crabs, genital crabs; misspelling: public lice

picture of crab, or pubic, louse

Crab, or pubic, louse soon after feeding (highly magnified). The red coloration is blood.

Pubic/crab lice bite to get blood. The bite leaves an intensely itchy lesion but, unlike some other blood-feeding insects (see below), pubic lice do not transmit diseases. Scratching to relieve the intense itch can result in secondary infections, however. Pubic lice are found worldwide and are frequently spread through sexual contact.


Crab lice eggs, or nits, on hairs

The eggs, or nits, of all human lice (head lice, body lice and crab lice) are about 1 mm long and are either glued onto individual hairs, as in head and crab lice, or are laid on clothing, as in body lice. Nits need body heat in order to hatch. Nits generally hatch in seven to ten days. Lice molt through several immature stages before becoming adults.

Treating pubic lice

Pubic lice, like head lice, do not live for long off their host so treatment of your home and clothing is not as important as treating the infestation itself. Treat pubic lice as you would head lice with medicated lice shampoo and nit combing (see How To Treat Lice and links above). Sexual partners of an infested person should be informed and possibly treated as well.


Other blood-feeding insect and mites


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Jack DeAngelis, PhD,  , email:  [email protected]

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