Pubic louse (also known as Crab louse)

Scientific Name: Pthirus pubis

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

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

Pubic louse (also known as Crab louse)

Natural Habitat

Exclusively on the human body, primarily in the pubic hair or coarse hair regions like eyelashes or armpits.

Diet & Feeding

Obligate ectoparasite; feeds exclusively on human blood several times a day.

Behavior Patterns

They are sedentary and move very slowly; they cling to hair shafts using crab-like claws and cannot jump or fly. They lay eggs (nits) on the hair shaft.

Risks & Benefits

Risks include intense itching (pruritus) due to an allergic reaction to their saliva, and skin discoloration known as maculae caeruleae. They are typically spread through close physical or sexual contact and require medical treatment to eradicate.

Identified on: 1/12/2026