Pubic Louse (Crab Louse)
Scientific Name: Pthirus pubis
Order & Family: Order: Psocodea (formerly Phthiraptera) | Family: Pthiridae
Size: 1.1 to 1.8 mm (about the size of a pinhead, slightly smaller than body or head lice)
Natural Habitat
Exclusively found on the human body, typically inhabiting coarse hair such as pubic hair, but occasionally eyelashes, eyebrows, beards, and chest hair.
Diet & Feeding
Hematophagous (feeds exclusively on human blood by biting the skin)
Behavior Patterns
They grasp coarse hairs with specialized crab-like claws. They are relatively sedentary compared to head lice, often remaining attached to the same hair shaft for long periods while feeding. They lay eggs (nits) cemented near the base of the hair shaft.
Risks & Benefits
Risks: Causes intense itching (pruritus) due to allergic reaction to saliva; scratching can lead to secondary bacterial skin infections. They do not spread disease but are indicators of close physical contact. Benefits: None known to humans or ecosystems in domestic settings.
Identified on: 2/17/2026