Head louse (nit)

Scientific Name: Pediculus humanus capitis

Order & Family: Order: Psocodea, Family: Pediculidae

Size: Nits (eggs) are 0.8 mm; adults are 2-3 mm (about the size of a sesame seed).

Head louse (nit)

Natural Habitat

The human scalp and hair shafts, particularly behind the ears and near the neckline.

Diet & Feeding

Obligate ectoparasites that feed exclusively on human blood several times a day.

Behavior Patterns

Nits are glued to hair shafts near the scalp. Moving adults crawl quickly but cannot jump or fly; they are spread through direct head-to-head contact.

Risks & Benefits

Causes intense itching (pruritus) and potential secondary skin infections from scratching; they do not spread bacterial or viral diseases but are a significant public health nuisance.

Identified on: 5/18/2026