What does a young louse look like? - briefly
A young louse, or nymph, is considerably smaller than the adult, translucent or pale in color, and lacks fully developed wings and reproductive structures. It retains the adult’s general body shape but appears lighter and less sclerotized.
What does a young louse look like? - in detail
A juvenile louse, often called a nymph, emerges from an egg (nit) and immediately resembles a miniature adult. Its body is elongated, flattened laterally, and covered with fine, translucent cuticle that gives a pale gray or off‑white hue. The head bears the same set of antennae as the adult, each consisting of five segments, but the sensory palps are proportionally shorter. Mouthparts are adapted for piercing skin and sucking blood; the stylet bundle is fully formed, though the feeding apparatus is slightly less robust than in mature specimens.
Key morphological traits of the nymphal stage include:
- Length: 1.0–1.5 mm for the first instar, increasing to 2.0–2.5 mm by the third instar.
- Color: translucent to light brown, darkening with each molt.
- Legs: six legs with clawed tarsi, each leg bearing two claws that grip hair shafts.
- Abdomen: segmented with visible dorsal and ventral plates; the dorsal sclerites are less sclerotized, giving a softer appearance.
- Eyes: rudimentary ocelli, functional but less pigmented.
Development proceeds through three instars before reaching adulthood. Molting is marked by the shedding of the cuticle, after which size, pigmentation, and sclerotization increase noticeably. The final molt produces a fully pigmented adult with hardened dorsal plates, enlarged mouthparts, and a reproductive system that is absent in the nymph.
Differences from the adult form are most evident in size, cuticular hardness, and coloration. The nymph lacks the fully developed genitalia and displays a lighter, more translucent exoskeleton, which gradually acquires the darker, opaque coloration characteristic of mature lice.