What do lice look like and what size are they? - briefly
Lice are tiny, wingless insects with a dorsoventrally flattened, reddish‑brown to grayish‑white body and six clawed legs. Their length varies from approximately 2 mm for head lice to 3–4 mm for body lice, with the largest specimens reaching about 8 mm.
What do lice look like and what size are they? - in detail
Lice are small, wing‑less insects belonging to the order Phthiraptera. Their bodies are laterally flattened, facilitating movement through hair or clothing fibers. The exoskeleton is smooth, lacking obvious segmentation, and is covered by a thin, translucent cuticle that often appears gray‑white, brown, or reddish depending on the blood content within the gut.
Size varies among the three common species:
- Head lice (Pediculus humanus capitis): adult length 2.2–3.6 mm, width about 1 mm; nymphs increase from 1 mm to adult size in successive molts.
- Body lice (Pediculus humanus corporis): adult length 3.0–4.5 mm, slightly broader than head lice; nymphs follow a comparable growth pattern.
- Pubic lice (Pthirus pubis): adult length 1.5–2.0 mm, noticeably broader relative to length, giving a “crab‑like” silhouette.
Eggs, called nits, are oval, 0.8 mm long, and adhere firmly to hair shafts or fibers with a cement‑like secretion. The operculum at one pole is visible as a tiny cap. Nits are often mistaken for dandruff but remain attached until hatching, typically after 7–10 days at ambient temperatures around 30 °C.
Morphological details aid identification:
- Antennae consist of five segments, ending in sensory cones.
- Six legs end in clawed tarsi, each bearing a small spine that grips hair.
- Mouthparts form a piercing‑sucking stylet, adapted for drawing blood from the host’s skin.
Coloration darkens after a blood meal, providing a temporary reddish hue. In unfed specimens, the cuticle appears more translucent, revealing underlying internal structures.
Understanding these dimensions and visual characteristics enables accurate detection and appropriate treatment of infestations.