Protura (subphylum Atelocerata, class Insecta) Subclass and order of minute (0.6–2 mm long), primitive, apterous, white insects, which lack eyes and antennae and have reduced, entognathous, piercing mouth-parts. Proturans are elongate, with segmented legs, the anterior pair used for sensory purposes, the middle and posterior pair for walking. The abdomen carries a pair of short styli (rudimentary limbs) on the basal three segments and the pseudocelli found on the head may represent antennal bases or postantennal organs. Species in this rare group live under bark, stones, or among rotting vegetation, and are sometimes subterranean in habit. Proturans exhibit anamorphosis, one extra segment being added at each moult. Metamorphosis is simple. There are 118 species, world-wide in distribution.

Protura An order of tiny wingless insects that live in soil and leaf litter. There are about 175 known species. The slender elongate adults are usually less than 2 mm long and lack eyes and antennae; the front pair of legs are held forwards as sensors. The mouthparts, which are largely entognathous (concealed within folds), are adapted for feeding on decaying organic matter. The young resemble the adults, but three segments are added to the end of the abdomen during development. The relationship of proturans to other arthropod groups is controversial. Although some authorities place them in the subclass Apterygota with the other wingless insects, other authors regard the Protura as a separate class within the superclass Hexapoda, most closely affiliated to the Collembola.