Why are lice red? - briefly
Lice look red because their translucent cuticle reveals the color of their hemolymph, which contains oxygen‑carrying pigments. These pigments give the insects a reddish appearance.
Why are lice red? - in detail
Lice display a reddish hue because their exoskeleton is thin and largely transparent, allowing the color of internal fluids to be visible. The primary factors are:
- Hemolymph composition – insect circulatory fluid contains hemoglobin‑like proteins that bind oxygen; the protein complex imparts a red coloration to the hemolymph.
- Blood ingestion – lice feed exclusively on host blood. After a meal, the gut is filled with fresh blood, which adds a bright red tint to the body.
- Cuticular translucency – the outer cuticle lacks heavy pigmentation; its translucence does not mask the color of the hemolymph or the ingested blood.
- Developmental stage – nymphs are almost colorless before feeding; they become increasingly red as they accumulate blood, which explains the variation in appearance among life stages.
The combination of a lightly pigmented cuticle, oxygen‑carrying hemolymph, and continuous blood consumption results in the characteristic red appearance observed in adult lice.