How do hair lice look? - briefly
Hair lice are tiny, wingless insects measuring 2–4 mm, with a flattened, elongated body and six legs ending in claw‑like tarsi. Their color ranges from gray‑white to tan, and their bodies are covered with fine, translucent hairs.
How do hair lice look? - in detail
Hair lice (Pediculus humanus capitis) are small, wing‑less insects that infest human scalp hair. Adult specimens measure 2–4 mm in length, roughly the size of a sesame seed, and possess a flattened, elongated body adapted for clinging to hair shafts. Their coloration ranges from gray‑white to light brown, often appearing translucent when observed under magnification.
Key visual features include:
- Head and thorax: The head is broader than the thorax, bearing six short, sturdy legs equipped with claw‑like tarsal hooks that grip individual hair strands. Antennae are short, typically three to four segments long, and may be difficult to see without a microscope.
- Abdomen: The abdomen consists of seven visible segments, each bearing fine, hair‑like setae that give the insect a slightly fuzzy appearance. The dorsal surface is smooth, while the ventral side is slightly concave to accommodate the host’s scalp.
- Coloration: Pigmentation is generally uniform, though freshly hatched nymphs appear paler and become darker as they mature. The exoskeleton may appear slightly glossy when illuminated.
- Movement: Lice move in a characteristic “crab‑like” fashion, using their hooked legs to crawl laterally along hair shafts rather than walking on the scalp surface.
Nymphal stages (first, second, and third instars) resemble miniature adults but are proportionally smaller, measuring 0.8 mm, 1.5 mm, and 2 mm respectively. Their bodies are less sclerotized, giving them a more translucent appearance. All stages share the same clawed leg structure and attachment behavior.
When examined with a handheld magnifier or a light microscope, the combination of size, flattened body, clawed legs, and the distinctive segmentation of the abdomen provides a reliable set of identifiers for hair lice.