Larvae engorge on host haemolymph and dissolved tissues for a period lasting from a few days to several months, depending on the taxon. Engorged larvae drop from the host back into the water. Thus parasitism serves not only a nutritional function for hydracarines, but it is the major means of dispersal and colonization of new habitats. Deutonymphs are usually less highly sclerotized than adults, which allows their integument to expand as they feed. The adult that emerges is also predatory and typically feeds on prey similar to that chosen by the deutonymph.
Adults are more highly sclerotized than deutonymphs, and have functional genital openings.
They are also often extremely sexually dimorphic, particularly those taxa in which the males transfer sperm directly to the female. One of the most striking things about water mites is their often brilliant colouration. Scarlet, orange, red and yellow mites are common, and are extremely visible against a background of green water plants. Discussion of Phylogenetic Relationships Based on current distributions of major taxa, water mites appear to have had a Pangaean origin, or to have evolved prior to the continental consolidation that resulted in Pangaea. There is also general acceptance of the Hygrobatoidea as being among the most derived of the superfamilies.