What does a louse and its nymph look like? - briefly
Adult lice are tiny, wingless insects about 2–4 mm long, with a flattened, elongated body, six short legs, and a gray‑brown coloration. Their nymphs look like miniature versions of the adult, measuring roughly 1–2 mm, with lighter color and underdeveloped features.
What does a louse and its nymph look like? - in detail
The adult louse is a small, dorsoventrally flattened insect measuring 2–4 mm in length, depending on species. Its body consists of a head, thorax, and abdomen, each covered by a tough, chitinous exoskeleton. The head bears a pair of short, slender antennae and prominent, laterally positioned compound eyes. Mouthparts form a piercing‑sucking stylet adapted for feeding on blood; the labium is concealed beneath the head capsule. The thorax supports three pairs of clawed legs, each ending in a pair of tarsal claws that cling tightly to hair shafts. The abdomen is segmented, with dorsal sclerites bearing fine, translucent hairs that give the insect a slightly glossy appearance. Color ranges from gray‑brown to reddish‑brown, often matching the host’s hair or skin tone.
Nymphal stages progress through three instars, each resembling a miniature adult. First‑instar nymphs are approximately 1 mm long, lacking full pigmentation and exhibiting a translucent, pale body. Their legs and antennae are proportionally smaller, and the mouthparts are not yet fully sclerotized. Second‑instar individuals increase to about 1.5 mm, develop darker cuticle, and display more defined segmentation, yet remain without developed genitalia. Third‑instar nymphs approach adult size (≈2 mm), possess nearly adult coloration, and have fully functional mouthparts, but their reproductive organs remain immature. Across all instars, the overall body shape, clawed legs, and attachment to host hair remain consistent, enabling rapid movement through the host’s integument.
Key morphological differences between adult and immature forms include:
- Size: adults 2–4 mm; nymphs 1–2 mm.
- Pigmentation: adults dark brown to gray; early nymphs pale and translucent.
- Reproductive structures: present only in mature individuals.
- Cuticle hardness: fully sclerotized in adults; progressively hardening through instars.
These characteristics allow precise identification of the insect at any developmental stage.