Arrenurus

Arrenurus (αρρεν - male, ουρά - tail) is a genus of water mites within the family Arrenuridae, and was first described by Antoine Louis Dugès in 1834. It has a cosmopolitan distribution in lentic waters, even on remote Pacific islands, and is found on every continent, with the possible exception of Antarctica. Some 950 species are currently recognised, making Arrenurus the largest of genera.

Arrenurus goes through seven stages - egg, inactive prelarva, larva, protonymph, deutonymph, tritonymph, and adult, only the larval stage being parasitic, and marked sexual dimorphism in the heavily sclerotised adults. Taxonomy of females is often problematic, but relatively simple in the males. Arrenurus larvae are ectoparasites of some aquatic insects in freshwater habitats, particularly the Odonata (Dragonflies and Damselflies). These mites establish an association for the purpose of transportation and nutrients, and attach to the host during the host's transition from larva to adult. Andrew et al. 2012, found that it is mainly Arrenurus species that are to be found on Odonata. Studies also show that parasitism by the mites affect the host's longevity and fecundity by draining its tissue fluids, hampering copulation and interfering with sperm transfer. Arrenurus larvae are also ectoparasites of Diptera and Coleoptera.