Entognathous Hexapods Collembola Protura and Diplura

Entognathous hexapods include two small taxa (class Diplura and Ellipura, order Protura) living in moist forest litter and a large group of springtails (class Ellipura, order Collembola) with at least 4000 species in terrestrial and semiaquatic environments. Most springtails live in moist terrestrial environments, but some colonize the surface film of quiet fresh and marine waters. They occur at densities much higher than almost any other invertebrate in soil litter. Unlike insects, springtails have only six abdominal segments, and cleavage of their eggs is total. Their name is derived from their ability to spring forward several centimeters when a forked structure (the furcula) flexed under the abdomen is rapidly uncocked. They have indirect fertilization, the young closely resemble adult Collembola, and adults continue molting throughout their lives (2—50+ molts). Springtails feed on decomposing organic matter or on microorganisms at the water surface. Proturans are completely terrestrial, their antennae have nearly atrophied away, and their front legs function somewhat like antennae. Diplurans are primitive hexapods whose ancestors may have given rise to both Protura and Collembola, and they are more closely related to insects than are ellipurans. Diplurans are blind and have two prominent abdominal cerci.

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