|
 Click photo to enlarge. Photo by Andrea Radwell. |
Taxonomy:
- Phylum Arthropoda
- Subphylum Chelicerata
- Class Arachnida
- Subclass Acari
- Order Acariformes
- Suborder Actinedida
- Cohort Parasitengonina
- Subcohort Hydrachnidiae
- Cohort Parasitengonina
- Suborder Actinedida
- Order Acariformes
- Subclass Acari
- Class Arachnida
- Subphylum Chelicerata
Hydrachnids (water mites) are an abundant, taxonomically diverse and ecologically important group of arachnids—the class that also includes spiders. They are found in virtually all types of freshwater habitats including cold and hot springs , streams and rivers, permanent and temporary ponds, lakes and brackish pools.
- Over 6,000 species have been recognized worldwide, and well over 1,500 species are currently estimated to occur in North America , north of Mexico .
- Approximately half of the North American species are not yet named, and many described species are known from only a few preserved specimens in collections.
- The water mite fauna of the southeastern United States is relatively poorly known but will undoubtedly prove to be a highly diverse assemblage. During the Pleistocene ice age, southern Appalachia and surrounding areas were important unglaciated refugia.
Water mites have a complex life history (see chart below).
- Throughout their lives, water mites are important in regulating the populations of various other invertebrates. Larval water mites parasitize hosts from a number of different insect orders including Diptera, Trichoptera, Plecoptera, Coleoptera, Hemiptera and Odonata. The parasitic relationship provides both nutrition for developing water mite larvae and the primary mechanism for water mite dispersal.
- Larvae remain attached for a period of feeding after which survival depends on detachment from the host into an aquatic habitat suitable for post larval development. Following detachment, engorged larvae enter a quiescent protonymph stage during which larval tissues are resorbed and the deutonymph develops. Deutonymphs, which resemble adults but are sexually immature, feed and increase substantially in size.
- When fully grown, they enter a second inactive period, the tritonymph stage, during which anatomical and morphological reorganization occurs to produce the adult.
- Deutonymphs and adults of many species prey on immature insects belonging to the same taxonomic groups whose adults they parasitize as larvae. Adults are slightly or strongly sexually dimorphic and males produce spermatophores which are transferred to females using pheremonal, behavioral and visual cues, often during elaborate courtship displays.
