Which appears first – lice or nits? - briefly
Nits (the eggs) are laid before any lice hatch, so the eggs appear first and then develop into lice.
Which appears first – lice or nits? - in detail
The life cycle of the human head louse proceeds in a fixed order: adult females deposit eggs on hair shafts, the eggs (commonly called nits) remain attached for a period of incubation, then hatch into nymphs, which mature into adults. Consequently, the egg stage precedes the presence of an adult insect.
Incubation of the egg lasts approximately 7–10 days under typical scalp conditions. During this time the egg is visible as a small, oval structure cemented to the hair. After the embryonic development completes, the nymph emerges, initially measuring about 1 mm and lacking full reproductive capacity. The nymph undergoes three successive molts over roughly 9–12 days before reaching adult size and fertility.
Key points:
- Egg deposition – adult female lays 5–10 eggs per day.
- Egg stage (nit) – 7–10 days, attached to hair, resistant to removal when firmly cemented.
- Nymph stage – 1 mm, immature, requires three molts.
- Adult stage – fully developed, capable of reproduction, lifespan about 30 days.
Because the egg must be laid before any louse can exist, the egg stage is always the first observable element in an infestation. Detection of nits therefore indicates that the life cycle has already begun, even if no adult insects are yet visible.