What do human lice and nits look like? - briefly
Human lice are tiny, wingless insects 2–4 mm long, gray‑brown, flattened, with six legs. Nits are oval, white‑to‑yellow eggs about 0.8 mm in length, firmly glued to hair shafts.
What do human lice and nits look like? - in detail
Human lice are small, wing‑less insects that measure 2–4 mm in length. Their bodies are flattened laterally, facilitating movement through hair shafts. The head‑lice species (Pediculus humanus capitis) exhibits a gray‑ish or tan coloration, with a translucent, oval abdomen. Six legs end in clawed tarsi, each bearing a pair of tiny hooks that grip hair. Eyes consist of simple ocelli, barely visible without magnification. The thorax bears three segments, each bearing a pair of legs; the abdomen contains twelve visible segments, some bearing tiny bristles. Body lice (Pediculus humanus humanus) are slightly larger, up to 4 mm, and display a more robust, reddish‑brown hue due to recent blood meals. Pubic lice (Pthirus pubis) differ markedly: they are broader, crab‑shaped, measuring about 1.5–2 mm, with a darker brown coloration and a pronounced, flattened body that resembles a miniature crab.
Nits are the eggs of these insects. They are ovoid, 0.8–1 mm long, and adhere firmly to the base of hair shafts using a cement‑like secretion. Freshly laid nits appear pale yellow or white; as embryos develop, the shells darken to a tan or brown shade. The egg is attached at an angle of roughly 30–45°, creating a characteristic “tilted” appearance. After hatching, the empty shell, called an “egg shell” or “casing,” remains attached for several days and can be distinguished by its smooth, translucent surface and lack of a viable embryo.
Key visual identifiers:
- Size: Lice 2–4 mm; nits ≤1 mm.
- Shape: Lice elongated (head, body) or crab‑shaped (pubic); nits oval.
- Color: Lice gray‑tan, reddish‑brown, or dark brown; nits pale to tan, darkening with age.
- Attachment: Nits fixed at an angle to hair shaft; lice move freely.
- Leg morphology: Six clawed legs on lice; nits lack limbs.
Microscopic examination (magnification 40×–100×) reveals detailed structures: lice display segmented abdomen and visible spiracles, while nits show a smooth chorion with a characteristic operculum at one pole, through which the nymph emerges. These visual traits enable accurate identification and differentiation among the three human‑lice species and their eggs.