There are approximately 60, 000 described species of mites, although this figure almost certainly represents less than 10% of the total diversity throughout the world. Mites are small-bodied arachnids that have adapted to a range of habitats, including deserts, tundra, forest canopy, freshwater and even deep ocean. Whereas there are numerous parasitic and commensal species on animals and plants, there are also many different species of free-living soil mites that have significant roles in decomposition and nutrient recycling. 

For such a diverse and important group of arthropods, mites are very poorly studied and understood. We still do not know if they represent a single lineage (Acari) or two distantly related lineages (Acariformes + Parasitiformes).

The approximately 150, 000 slide mounted mites of the FSCA represents one of the largest mite collections in North America. This collection includes almost 800 type specimens, of which approximately two thirds are phytoseiids, an important group of predatory mites used in the biological control of spider mites and other plant parasitic mites.