Pubic Louse (also known as Crab Louse)

Scientific Name: Pthirus pubis

Order & Family: Order: Psocodea; 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

Found exclusively on humans, specifically in coarse hair such as pubic, armpit, chest, or facial hair (eyelashes/eyebrows in children).

Diet & Feeding

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

Behavior Patterns

They do not jump or fly; they crawl from hair to hair and are mostly transmitted through close physical contact. They use their crab-like claws to anchor onto hair shafts close to the skin.

Risks & Benefits

Risk: Intense itching (pruritus) due to an allergic reaction to their saliva, and small blue-gray skin spots (maculae caeruleae). They are not known to transmit diseases. Benefit: None to humans or the ecosystem.

Identified on: 1/8/2026