How do human head lice look? - briefly
Human head lice are tiny, wing‑less insects about 2–4 mm long, with a flat, elongated body that appears grayish‑white or tan and is divided into head, thorax, and abdomen; each adult has six legs ending in claw‑like tarsi for gripping hair shafts. Their bodies are covered with tiny, translucent scales that give a slightly mottled appearance when viewed close up.
How do human head lice look? - in detail
Human head lice (Pediculus humanus capitis) are tiny, wing‑less insects measuring 2–4 mm in length when fully grown. Their bodies are flattened laterally, which enables them to move easily through hair shafts. The head is broader than the thorax, giving the insect a roughly “spoon‑shaped” silhouette.
The exoskeleton is semi‑transparent, allowing the underlying hemolymph to give a pale yellow‑brown hue. In unfed specimens, the coloration appears lighter; after blood meals, the abdomen expands and turns a darker reddish‑brown due to ingested blood. The abdomen is segmented into three visible sections, each bearing small, fine hairs (setae) that lie flat against the surface.
Six legs emerge from the thorax, each ending in a claw‑like tarsus. The claws are curved and adapted for gripping individual hair strands; they are spaced approximately 0.2 mm apart, matching the average hair diameter. The legs also possess sensory hairs that detect vibrations and temperature changes.
Eyes are present as two simple, dark pigmented ocelli positioned on the head, providing basic light perception. Antennae are short, segmented, and concealed beneath the head capsule when the louse is at rest.
Nymphal stages resemble adults but are smaller (1–2 mm) and lack fully developed reproductive organs. Their coloration remains lighter, and the abdomen is less engorged. All stages exhibit the same body plan, leg structure, and claw arrangement, which are critical for navigating the host’s scalp.
Key visual identifiers:
- Size: 2–4 mm (adult), 1–2 mm (nymph)
- Body shape: laterally flattened, spoon‑shaped head
- Color: translucent pale yellow‑brown, darkening after feeding
- Abdomen: three visible segments with fine setae
- Legs: six, each ending in a curved claw spaced for hair grip
- Eyes: two dark ocelli on the head
- Antennae: short, concealed
These characteristics enable reliable identification of head lice during visual inspection of hair and scalp.