The order Collembola (springtails) contains small hexapods, with body lengths usually in the range of a few millimeters reaching 1.5 cm in some extreme cases. With 9000 described species worldwide springtails form the largest class in the Entognatha group (compare: Diplura ~500, Protura ~750), but they are far from the diversity of insects (> 1 million sp.). A typical feature of springtails is the furcula, an appendage of the 4th abdominal segment, which is held beneath the body of the springtail. However if disturbed, springtails may release their spring-like "tail" which will result in them being lifted of the ground and thrown through the air. Evidently, this features gave this order its name.
