Mites are small arachnids, eight-legged arthropods, of two large orders, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari. The cited article says that most recent genetic analyses do not recover the two as each other closest relative within Arachnida, rendering the group invalid as a clade, that most mites are tiny, less than one millimetre in length, with a simple unsegmented body plan, and that some species live in water, many live in soil as decomposers and others live on plants, sometimes creating galls. It is the mite half of the combined insect or mite value. Pests and diseases recorded in the atlas as caused by a mite are grouped under this concept.