What is a small louse called? - briefly
A small louse is referred to as a nit. The term denotes the egg or early nymph stage of the insect.
What is a small louse called? - in detail
Lice belong to the order Phthiraptera and are obligate ectoparasites of mammals and birds. Adult specimens range from 1 to 4 mm in length, but individuals at the earliest developmental stages are considerably smaller.
The first stage after the egg (commonly called a nit) is an immature form known as a nymph. Nymphs resemble adults in shape but lack fully developed genitalia and are typically half the size of mature lice. They undergo three successive molts, each stage still referred to as a nymph, before reaching adulthood.
Key terminology for the tiny stages:
- Nit – the egg attached to hair shafts; size about 0.5 mm.
- First‑instar nymph – newly hatched, translucent, approximately 0.3 mm.
- Second‑instar nymph – larger, opaque, around 0.5 mm.
- Third‑instar nymph – near adult size, 0.8–1 mm, still incapable of reproduction.
Collectively, these immature forms are described as “nymphs” or “juvenile lice.” The term applies to all three instars and distinguishes them from the fully mature, reproductively active insects.
In scientific literature, the phrase “nymph” is preferred over informal expressions such as “baby louse” because it conveys the precise developmental status within the hemimetabolous life cycle of lice.