Lice on a person: how do they look? - briefly
Adult head lice measure 2–3 mm, appear gray‑white, and have a flattened, crab‑like body with six legs, the front pair specialized for clinging to hair shafts. Nymphs share this shape but are smaller and initially translucent until they ingest blood.
Lice on a person: how do they look? - in detail
Human‑infesting lice are tiny, wingless insects measuring 2–4 mm in length. Their bodies are flattened laterally, facilitating movement through hair shafts. The head‑lice (Pediculus humanus capitis) exhibits a gray‑brown hue; the exoskeleton appears translucent when alive, becoming more opaque after feeding. Antennae consist of six segments, each tipped with sensory cones. Six legs end in curved claws that grasp individual strands of hair.
Body‑lice (Pediculus humanus corporis) share the same size range but possess a slightly darker, reddish‑brown coloration. Their thorax is broader, allowing them to navigate coarse body hair and clothing fibers. Pubic‑lice (Pthirus pubis) are broader and crab‑shaped, measuring about 1.5–2 mm. Their posterior legs are markedly longer, adapted for clinging to coarse hair in the genital area.
Eggs, commonly called nits, are oval, 0.8 mm long, and firmly attached to hair shafts about 1 cm from the scalp. Nits appear white or yellowish, often resembling dandruff but remain immobile. After hatching, nymphs resemble miniature adults, lacking fully developed reproductive organs; they undergo three molts over a week before reaching maturity.
Visible signs include:
- Live insects moving slowly across the scalp or body hair.
- Small, rust‑colored spots where lice have fed, indicating blood ingestion.
- Irritation or itching caused by saliva injection during feeding.
- Clusters of nits aligned along the hair shaft, often at a uniform angle.
Detection is most reliable with a fine‑toothed comb applied to damp hair, allowing the comb to capture both adults and nits. Under magnification, lice display a distinct head with compound eyes and bristle‑like setae covering the abdomen. Their color may darken after a blood meal, providing a brief visual cue before returning to a translucent state.