How do head lice look up close? - briefly
Under magnification, a head louse appears as a flattened, oval insect about 2–3 mm long, gray‑brown in color, with six legs ending in clawed tarsi that grip hair shafts. Its head bears a pair of antennae and compound eyes, while the thorax shows distinct segmentation and the abdomen is covered with tiny, translucent scales.
How do head lice look up close? - in detail
Head lice (Pediculus humanus capitis) are tiny, wing‑less insects measuring 2–4 mm in length. The body is elongated and flattened laterally, allowing it to move easily through hair shafts. The dorsal surface is covered by a thin, translucent cuticle that appears light gray to brownish when viewed under magnification. Fine, irregularly spaced hairs (setae) line the exoskeleton, giving the organism a slightly fuzzy appearance.
The head bears a pair of compound eyes composed of numerous ommatidia, each visible as tiny dark spots. Antennae consist of five segmented rods, each segment tapering toward the tip and bearing sensory receptors for chemical cues. Mouthparts form a piercing‑sucking apparatus: a short labium houses a stylet that can be seen as a thin, needle‑like structure positioned ventrally.
Three pairs of legs extend from the thorax. Each leg ends in claw‑like tarsi equipped with a single, backward‑curving hook that grips individual hair strands. The legs are relatively short, each segment clearly demarcated, and display a pale, membranous appearance.
The abdomen is composed of seven visible segments. Each segment bears a pair of spiracles—small, circular openings for respiration—visible as tiny dark dots along the lateral margins. In mature specimens, the abdomen may contain small, opaque eggs (nits) attached to the hair shaft near the scalp; these eggs appear as oval, whitish bodies measuring about 0.8 mm.
Nymphs, the immature stages, resemble adults but are smaller (1–2 mm) and lack fully developed reproductive organs. Their cuticle is more translucent, making internal structures such as the gut visible as faint, reddish lines when illuminated.
Eggs (nits) are oval, about 0.8 mm long, with a smooth, glossy surface. The operculum—a tiny cap at one end—can be seen as a slight indentation. The shell is semi‑transparent, allowing observation of the developing embryo inside, which appears as a dark speck that grows darker as the nymph matures.
Overall, microscopic examination reveals a compact, segmented arthropod with distinct sensory organs, clawed legs adapted for grasping hair, and a reproductive system that produces characteristic oval eggs firmly cemented to the host’s hair.