What do lice and fleas look like on a human? - briefly
Lice are tiny, wing‑less insects about 2–4 mm long, pale‑brown to gray, and are seen attached to hair shafts with their nits glued close to the scalp. Fleas are slightly larger (1.5–4 mm), dark brown, smooth‑bodied, and appear as moving specks on clothing or skin, often leaving small, red bite marks.
What do lice and fleas look like on a human? - in detail
Lice that infest a person are small, wing‑less insects belonging to three species. The head louse (Pediculus humanus capitis) measures 2–3 mm in length, has a flattened, elongated body, and appears grayish‑white to brown. Its posterior abdomen is broader than the head, giving a “tapered‑to‑wide” silhouette. The body louse (Pediculus humanus humanus) is slightly larger, 3–4 mm, with a similar coloration but a more robust abdomen and a pronounced dorsal keel. The crab louse (Pthirus pubis) is broader, 1.5–2 mm, and resembles a tiny crab; its body is rounder, legs are longer and spread sideways, and coloration ranges from pale gray to reddish‑brown.
Fleats that bite humans are generally larger than lice. The human flea (Pulex irritans) measures 2–4 mm, has a laterally flattened body, dark brown to black coloration, and a hard, shiny exoskeleton. The cat flea (Ctenocephalides felis), frequently found on people in close contact with pets, measures 1.5–3 mm, is reddish‑brown, and exhibits a distinctive “hopping” posture due to enlarged hind legs.
Key visual characteristics:
- Size: lice 2–4 mm; fleas 1.5–4 mm.
- Body shape: lice elongated and flattened; crab louse round with lateral legs; fleas laterally compressed with strong hind legs.
- Color: lice gray‑white to brown; crab louse pale to reddish‑brown; fleas dark brown to black or reddish‑brown.
- Location on the host: head lice cling to scalp hair, laying eggs (nits) on shafts; body lice reside in clothing seams, moving to skin to feed; crab lice inhabit pubic and other coarse hair regions. Fleas prefer warm, moist areas such as ankles, legs, and the waistline, often after contact with infested animals.
- Movement: lice crawl slowly, rarely jumping; fleas jump several centimeters, creating sudden, brief bites.
Recognizing these morphological details enables accurate identification and appropriate treatment.