Head Louse

Scientific Name: Pediculus humanus capitis

Order & Family: Order: Psocodea (formerly Phthiraptera); Family: Pediculidae

Size: 2.0 mm to 3.5 mm (roughly the size of a sesame seed)

Head Louse

Natural Habitat

Exclusively the human scalp and hair strands, primarily near the scalp for warmth and access to blood.

Diet & Feeding

Obligate hematophagy; they feed exclusively on human blood several times a day.

Behavior Patterns

They are wingless and cannot jump; transmission occurs primarily through direct head-to-head contact. Females glue eggs (nits) to hair shafts near the scalp. They cannot survive for more than 24-48 hours away from a human host.

Risks & Benefits

Risks include intense itching (allergic reaction to saliva), scalp irritation, and potential secondary bacterial infections from scratching. They do not spread disease. There are no ecological benefits as they are specialized parasites.

Identified on: 3/24/2026