What do domestic lice look like? - briefly
Domestic lice are tiny, wingless insects about 2–4 mm long with a flattened, oval body that ranges from gray‑brown to reddish‑brown, a short head bearing antennae, and six legs ending in clawed tarsi for gripping hair shafts. Their eyes are reduced, and they lack wings, making them well‑adapted to living close to the scalp or body hair of humans.
What do domestic lice look like? - in detail
Domestic lice are small, wing‑less insects that thrive on human hosts. Adults measure 2–4 mm in length; females are slightly larger than males. The body is dorsally flattened, covered with fine, translucent cuticle that appears gray‑brown to reddish‑brown depending on blood content. The head bears a pair of short antennae with five segments, each ending in a sensory organ. Mouthparts are adapted for piercing skin and sucking blood, forming a robust, curved proboscis.
Legs are three‑segmented, each ending in a single claw that allows the louse to grasp hair shafts or clothing fibers. The claws are sharp, curved, and positioned laterally on the tarsus. The abdomen consists of nine visible segments; the posterior segments are enlarged in females to accommodate egg production. Coloration of the abdomen may darken after a blood meal, giving a temporarily reddish hue.
Nymphal stages resemble adults but are smaller (1–2 mm) and lack fully developed genitalia. Six instars occur, each molting to increase size and acquire more defined anatomical features. Nymphs retain the same body shape and coloration, though they appear paler before feeding.
Eggs, commonly called nits, are oval, 0.8 mm long, and firmly attached to hair shafts or fabric fibers by a cement‑like secretion. The shell is opaque, ranging from white to yellow‑brown, and the operculum (cap) is visible at one pole. Eggs hatch after 7–10 days, releasing a nymph that immediately seeks a blood meal.
Two principal species inhabit domestic environments: the head louse, which prefers scalp hair, and the body louse, which resides in clothing and moves to the skin to feed. Both share the morphological traits described above, differing mainly in habitat preference and slight variations in coloration and size. «Pediculus humanus capitis» typically exhibits a darker dorsal surface than «Pediculus humanus corporis», reflecting adaptation to differing microhabitats.