Pubic Louse (Crab Louse)

Scientific Name: Pthirus pubis

Order & Family: Order: Psocodea (formerly Anoplura); Family: Pthiridae

Size: 1.1 mm to 1.8 mm (roughly the size of a pinhead)

Pubic Louse (Crab Louse)

Natural Habitat

Coarse human body hair, primarily in the pubic region, but occasionally found in eyelashes, eyebrows, beards, or chest hair.

Diet & Feeding

Obligate blood-feeders; they consume human blood exclusively several times a day.

Behavior Patterns

They are sedentary parasites that grasp hair shafts with specialized, crab-like claws. They cannot jump or fly and are usually transmitted through close physical contact. Eggs (nits) are glued to the base of hair shafts.

Risks & Benefits

Risks: Causes intense itching (pruritus) due to an allergic reaction to their saliva; can cause secondary skin infections from scratching and characteristic bluish spots (maculae caeruleae). No known benefits.

Identified on: 1/11/2026