Springtails are tiny insects in the order Collembola, a relatively ancient and primitive group in the sub-class of wingless insects known as Apterygota. Springtails have a fossil record extending back to the Devonian era, some 400 million years ago. Collembolans undergo complete metamorphosis, where the immature stages (nymphs) are tiny representations of the adult.
Springtails are named for their method of locomotion when disturbed, springing high into the air. This mechanism involves a ventral "spring" (the furculum) on one of the abdominal segments, which is locked into a "catch" on another segment. When this mechanism is activated by a frightened springtail, it can propel the tiny animal as far as 1.6-2 in (4-5 cm). This distance is many times its body length, enabling the springtail to escape its predators, which are mostly soil-dwelling mites, tiny relatives of spiders.
Springtails occur on all continents, living in soil and organic debris, or on the surface of non-flowing water. Springtails eat decaying organic matter and tender plant tissues, as well as sucking plant juices, or feeding on fungi and bacteria. Springtails can be enormously abundant in soils, with as many 300-600 animals/in3 in good habitat, making populations of billions per acre.
Springtails are not often serious pests. One species, the garden springtail (Bourletiella hortensis), sometimes causes significant damage to tender, recently germinated seedlings of agricultural or horticultural plants. Often, springtails occur in damp places in homes, or in the potting medium of house plants, where they can be seen as tiny, white specks jumping about on the surface. However, springtails do not do any damage in these domestic situations.
Many species of springtails are active during winter. Some of the forest species migrate to the surface of the snowpack, where they bask and jump about in the winter or early spring sunlight and forage for spores and organic debris. A common species with this habit is the tiny, 0.08 in (2 mm) long, dark-colored snow flea (Hypogastrura nivicola) of eastern North America and Europe.