[3] Water mites may be brilliant red or orange in colour, unusual among freshwater invertebrates, but they also display more subtle blues, greens and yellows.

They are also unusual among mites in some lineages having movable, internalized eye lenses sunk deep within the prosoma rather than being set on the surface of the cuticle.

In post-larval stages, there are complex dermal structures consisting of a gland paired with a sensory seta (glandularia), possibly for defense against predators.

[6] Typical habitats include streams and marshes, but they may also be found in more obscure areas such as treeholes, hot springs, deep lakes and waterfalls.

[8] It was originally believed that water mite larvae located hosts by accidental contact, but recent studies have found they likely utilize a combination of visual, tactile, and chemical cues.

[9] The abundance of water mites in a region, as well as prevalence and intensity of host infection, are impacted by a multitude of environmental and biological factors, and have shown great geographic variation.

[17][9][10] These mites are typically abundant along the margins of temporary ponds, springs, streams, and seepage areas in North America and Europe.

Mullen hypothesized that this life history strategy increased chances of mite survival two-fold because those parasitizing males would likely die before returning to a suitable adult habitat.

Females lay eggs in protected areas hidden among the abundant vegetation of these habitats, and upon hatching, larvae can be found swimming throughout the upper water column in search of hosts.

[15] Even though Arrenurus mite larvae have been considered as potential biocontrol agents, unrealistic numbers would need to be released in order to prove effective on their own.

They prey on other water mites, small crustaceans (e.g. cladocerans, ostracods and copepods), the eggs, larvae and pupae of aquatic insects, and non-arthropod invertebrates such as rotifers, nematodes, and oligochaetes.

To feed, water mites bite prey, inject saliva containing digestive enzymes to liquefy the tissue, and suck out the liquid.