Pubic Louse (commonly known as "Crabs")

Scientific Name: Pthirus pubis

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

Size: Typically 1.1 mm to 1.8 mm in length (smaller than head or body lice).

Pubic Louse (commonly known as "Crabs")

Natural Habitat

Exclusively found on the course hair of humans, typically in the pubic region, but occasionally found on eyelashes, eyebrows, beard, mustache, and armpit hair.

Diet & Feeding

Hematophagous (blood-sucking); they feed exclusively on human blood.

Behavior Patterns

They grasp hair shafts with specialized, crab-like claws on their second and third pairs of legs (which gives them their nickname). They are relatively immobile compared to head lice, typically staying attached near the skin to feed frequently.

Risks & Benefits

Risks: They cause intense itching (pruritus) due to an allergic reaction to their saliva. Scratching can lead to secondary bacterial skin infections. They do not typically transmit diseases, unlike body lice.

Identified on: 3/11/2026