The class Collembola, which contains semi-aquatic species, was formerly included in the Apterygota, a primitive subclass of Insecta. Recent taxonomic works generally treat Collembola as a separate class and recognize from one to five orders. Three fami lies of Collembola have genera with semiaquatic species. Collembolans are wingless.
Collembolans are ametabolous, i.e. with no metamorphosis.
They occur on the surface of both lentic and lotic waters, and submerge only accidentally. They tend to leap off the surface of the water when disturbed, hence collecting specimens may be tricky. Reported to feed on detritus, algae, fungi, or dead animal matter, semiaquatic collembolans typically specialize on the particular foods available on the water surface. The mouthparts of some species are modified for consuming the lipoprotein layer of the surface film or the underlying bacterial populations. All collembolans are characterized by the collophore on the venter of the first abdominal segment.