; subphylum Uniramia, class Insecta)
Subclass and order of primitive, eyeless, wingless, small insects, exhibiting simple metamorphosis, which have entognathous, biting mouth-parts, short antennae, six-segmented abdomens (sometimes fused), and legs which lack tarsi (see tarsus). Most species are less than 6 mm long, and can leap by means of a special, forked, springing organ (the furcula) which is held up against the under side of the abdomen by a catch (retinaculum, hamula, ventral tube, or collophore): when the furcula is moved downwards suddenly, it hits the substrate and propels the animal through the air. There are two suborders, the elongate Arthropleona, and the globular Symphypleona whose members have the mouth-parts tucked under the head. Springtails occur throughout the world and live in soil, leaf-litter, under bark and decaying wood, and among fungi and vegetation, and are very common, attaining densities of 60 000/m2. Some species are pests of leguminous crops, some feed on the blood of vertebrates, but most are important as scavengers and agents of nutrient recycling. Some species live on the water surface of ponds, or even on alpine snowfields where they feed on pollen and other debris. There are about 2000 species.
Subjects: Zoology and Animal Sciences.