How do lice look under the skin? - briefly
Lice stay on the scalp’s surface, clinging to hair shafts as small, flattened, gray‑brown insects roughly the size of a sesame seed. They do not burrow into the skin, so they are never visible beneath the epidermis.
How do lice look under the skin? - in detail
Lice are external parasites that cling to hair shafts and skin surfaces; they do not burrow beneath the epidermis. When a person inspects an infested area, the insects appear as tiny, mobile, flattened arthropods. Adult head lice measure 2–3 mm in length, have a cigar‑shaped body, and display a gray‑white coloration that may appear slightly translucent against the scalp. Their three pairs of legs end in claw‑like tarsal hooks, allowing firm grasp of individual hairs. The head bears a pair of antennae, each composed of six segments, and a pair of compound eyes that are visible only under magnification. The abdomen consists of seven visible segments, each bearing minute bristles (setae) that give a faintly fuzzy outline.
Nymphs, the immature stages, resemble adults but are proportionally smaller—approximately 1 mm when newly hatched and reaching 2 mm at the final instar. Their color ranges from pale translucent to the same gray‑white as adults, becoming darker as they mature. Nits (eggs) are oval, about 0.8 mm long, and firmly attached to the hair shaft about 1 mm from the scalp. Their shells are smooth, white to yellowish, and become more opaque as the embryo develops.
Body lice, which inhabit clothing seams but move onto the skin to feed, are slightly larger (3–4 mm) and have a broader abdomen. Their coloration is a dull gray‑brown, often appearing darker after blood meals. Pubic lice (Pthirus pubis) are broader and shorter, roughly 1.5–2 mm, with a crab‑like silhouette due to robust, laterally positioned legs. Their bodies are darker, ranging from brown to reddish after feeding.
Key visual cues for identification:
- Size: 1–4 mm depending on species and developmental stage.
- Shape: elongated and flattened for head and body lice; broader, crab‑like for pubic lice.
- Color: gray‑white (head lice), gray‑brown (body lice), brown‑red (pubic lice).
- Legs: three pairs with clawed tarsi; pubic lice have prominently set lateral legs.
- Eggs: oval, firmly glued to hair, white to yellow, 0.8 mm long.
Under magnification, the ventral side reveals a set of spiracles (breathing openings) arranged in a line on each side of the abdomen. The dorsal surface shows a series of small, raised plates (tergites) that may be slightly pigmented. Blood meals cause the abdomen to expand and the body to appear more engorged, giving a darker hue.
In summary, lice are visible on the skin as small, flat insects with characteristic size, shape, coloration, and leg morphology. Their eggs appear as firmly attached, oval shells on hair shafts. No evidence supports sub‑epidermal habitation; all observable structures reside on the surface.