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Insect identification > Collembola
The Collembola are usually very small insects and, being dark colored inmost cases, are not often noticed. Most of this group have a "spring" attached near the hinder end of the body beneath. This consists of a single piece to which a pair of others are joined and the whole is carried pointing forward when not in use. When the spring is suddenly pressed against the ground, the entire body of the insect is thrown into the air and a peculiar hopping or leaping motion results. On the underside of the first abdominal segment is the collophore, an organ very differently developed in different species. It secretes a sticky fluid which aids the insect in holding on to smooth surfaces.
The Collembola may be described as
Apterygota without styli on the underside of the abdomen; cerci absent or very small; abdomen of six segments, often so much condensed as hardly to show that number; with a variously developed collophore on the first abdominal segment beneath; with a ventral spring in most cases; insects usually much smaller than the Thysanura.
Familiar members of this order are the snow fleas sometimes seen in enormous numbers on snow, where their dark color and hopping movements make them very noticeable.
The greatest injury caused by these insects is to tender plants, especially seedlings, and to mushrooms. They make tiny holes in the leaves, stems and roots in different cases; destroy root hairs and small rootlets and make places where spores of fungi and bacteria can enter. With mushrooms they feed on the mycelium and also on the stems and caps, sometimes ruining them completely.
Folsom states that about two thousand species of Collembola have been described.