The Hydrachnidia are not the only aquatic mites, but they are the most successful group of mites found in freshwater. The mites form a considerable part of the lasiophil fauna.
Many water mites exhibit bright colour patterns, containing greens, blues, oranges or reds.
Fish and invertebrates will eat water mites, but the brightly coloured species are apparently distasteful and predators learn to reject them. The Hydrachnidia are among the most numerically abundant and taxonomically diverse of the freshwater aquatic mites. Presumably, when the Chironomidae underwent rapid species radiation, so did the species of mites that parasitized them. This trait adds energy from a different resource and minimizes competition between instars. The ability to swim, restricted among mites to species of Hydrachnidia, greatly contributes to their dispersal and allows for a broader diversity of life styles.