Mite

Mites are small arachnids (eight-legged arthropods). Mites span two large orders of arachnids, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari. However, most recent genetic analyses do not recover the two as each other's closest relative within Arachnida, rendering the group non-monophyletic. Most mites are tiny, less than in length, and have a simple, unsegmented body plan. The small size of most species makes them easily overlooked; some species live in water, many live in soil as decomposers, others live on plants, sometimes creating galls, while others again are predators or parasites. This last type includes the commercially destructive Varroa parasite of honey bees, as well as scabies mites of humans. Most species are harmless to humans, but a few are associated with allergies or may transmit diseases. The scientific discipline devoted to the study of mites is called acarology. The mites are not a defined taxon, but is used for two distinct groups of arachnids, the Acariformes and the Parasitiformes. The phylogeny of the Acari has been relatively little studied, but molecular information from ribosomal DNA is being extensively used to understand relationships between groups. The 18 S rRNA gene provides information on relationships among phyla and superphyla, while the ITS2, and the 18S ribosomal RNA and 28S ribosomal RNA genes, provide clues at deeper levels. Superorder Parasitiformes – ticks and a variety of mites Opilioacarida – a small order of large mites that superficially resemble harvestmen (Opiliones), hence their name Holothyrida - small group of predatory mites native to former Gondwana landmasses Ixodida – ticks Mesostigmata – a large order of predatory and parasitic mites Trigynaspida - large, diverse order Monogynaspida - diverse order of parasitic and predatory mites Sejida - small order of mites containing five families Superorder Acariformes – the most diverse group of mites Endeostigmata (probably paraphyletic) Eriophyoidea – gall mites and relatives Trombidiformes – plant parasitic mites (spider mites, peacock mites, red-legged earth mites, etc.