Appearance - This insect is easily differentiated from the head louse and body louse by the strong thick claws of the mid and hind legs, while the claws of the fore legs are long and fine. The body is broader than long, contrasting with both other species of Pediculus humanus.
Life cycle - The egg is slightly smaller than that of Pediculus and it is glued to a body hair with more cement. The egg hatches in 7 - 8 days. The three nymphal stages do not wander far from the hair, which is grasped with the tarsal claws. Several hours are usually taken to complete each bloodsucking meal. They occasionally are found on eye lashes and eye brows.
The nymphs become adults in from 13 - 17 days and it seems probable that the length of adult life is not more than one month. Fewer eggs are laid than Pediculus. The adult is thought to be unable to survive longer than 24 hours when removed from its host.
Crab lice usually die within 24 hours if separated from their host. This short survival and their sluggish movement inhibit the spread of crab lice, except through intimate (sexual) personal contact or in extremely crowded living and sleeping conditions where they can and do spread readily. Crab lice may be (but rarely are) spread by nits on loose hairs left on bedding, towels and toilets by infested persons.
Crab or Pubic Lice Overview
Adult crab lice are only a little over half the size of body or head lice, rarely more than 1/12" long; their last two pairs of legs terminate in hooked mitts that resemble crab claws. These lice are confined to coarse pubic hair and sometimes armpits, eyebrows and eyelashes. Pubic lice move very little in the pubic region and produce few eggs. The most common method of transmission of crab or public lice is by sexual intercourse. When infested pubic hair detaches, lice can hatch on underwear, towels, in beds, or on toilet fixtures. If their immediate environment is above 50o F., a pair of pubic lice could infest another person without personal contact.
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