Pthirus pubis

Pthirus pubis (Linnaeus, 1758)

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Brief Summary

The Pubic (or Crab) Louse (Pthirus pubis, often incorrectly spelled Phthirus pubis) is an insect in the Order Psocodea (parasitic lice, formerly Order Phthiraptera, plus bark lice, formerly Order Psocoptera). Pubic Lice are ectoparasites with humans as the only host.They are found throughout the world.

Pubic lice have three stages: egg, nymph and adult.  Eggs (nits) are laid on a hair shaft.  Females will lay approximately 30 eggs during their 3-4 week life span.  Eggs hatch after about a week and become nymphs, which look like smaller versions of the adults.  The nymphs undergo three molts before becoming adults.  Adults are 1.5-2.0 mm long and flattened.  They are much broader in comparison to head and body lice.  Adults are found only on the human host and require human blood to survive.  If adults are forced off the host, they will die within 24-48 hours without a blood feeding.  Pubic lice are transmitted from person to person most commonly via sexual contact, although fomites (bedding, clothing) may play a minor role in their transmission.

(Centers for Disease Control Parasites and Health website)

Author(s): Shapiro, Leo
Rights holder(s): Shapiro, Leo


  • Phthirus pubis (Linnaeus, 1758) (synonym)