Louse (Head Louse or Body Louse)

Scientific Name: Pediculus humanus capitis (Head Louse) or Pediculus humanus humanus (Body Louse)

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

Size: 2 to 3 millimeters long (about the size of a sesame seed).

Louse (Head Louse or Body Louse)

Natural Habitat

Exclusively on the human body; head lice are found on the scalp hair, while body lice live in clothing and bedding but move to the skin to feed.

Diet & Feeding

Hematophagous (feed exclusively on human blood several times a day).

Behavior Patterns

They are obligate parasites that cannot fly or jump. They move by crawling rapidly along hair shafts using claw-like legs specialized for grasping. They lay eggs (nits) glued firmly to the base of hair shafts.

Risks & Benefits

Risks: They cause intense itching (pruritus) and social stigma. Scratching can lead to secondary bacterial skin infections. Body lice (but not head lice) are vectors for diseases like typhus, trench fever, and relapsing fever. Benefits: None known to humans.

Identified on: 2/8/2026