Crab Louse (or Pubic Louse)
Scientific Name: Pthirus pubis
Order & Family: Order: Psocodea (Suborder: Anoplura); Family: Pthiridae
Size: 1.1 mm to 1.8 mm (about the size of a pinhead)
Natural Habitat
The coarse hair of the human body, most commonly the pubic region, but can also be found in armpits, beards, and eyelashes.
Diet & Feeding
Obligatory hematophages: they feed exclusively on human blood several times a day.
Behavior Patterns
They are relatively immobile and spend their entire life cycle on the host. They use their specialized claws to grasp onto thick hair shafts and lay eggs (nits) at the base of the hair.
Risks & Benefits
No known benefits. Risks include intense itching (pruritus) due to an allergic reaction to their saliva, and small blue spots on the skin from feeding. They do not generally transmit diseases but can cause secondary skin infections from scratching.
Identified on: 3/9/2026