Pubic Louse (Crab Louse)

Scientific Name: Pthirus pubis

Order & Family: Order: Psocodea (formerly Phthiraptera), Family: Pthiridae

Size: 1.1 to 2.0 millimeters (very small, slightly smaller than a sesame seed)

Pubic Louse (Crab Louse)

Natural Habitat

Exclusively inhabits coarse human body hair, primarily in the pubic region, but occasionally in eyelashes, eyebrows, beards, armpits, and chest hair.

Diet & Feeding

Hematophagous; they feed exclusively on human blood by biting the skin.

Behavior Patterns

They grasp coarse hair shafts with their specialized claws (which resemble crab claws, hence the common name) and remain relatively stationary, feeding frequently on blood. They are transmitted primarily through close physical contact.

Risks & Benefits

Risks: Causes intense itching (pruritus due to an allergic reaction to saliva), skin irritation, spread of secondary bacterial infections due to scratching, and psychological distress. They are not known to transmit diseases. Benefits: None.

Identified on: 3/6/2026