Oribatida

Oribatida, or oribatid mites, are an order of mite, and the oldest mite group, found present in fossils over 400 million years ago.

Abundance and Diversity

Oribatid mites are distributed worldwide, and are commonly found at a density of 50,000 to 500,000 individuals per square meter in soils. Oribatid mites are known to predominate over other groups of mites and mesofauna in most soils. They live in all terrestrial ecosystems, including the arctic and the tropics.

Coniferous forests typically have the highest numbers of oribatid mites, followed by deciduous hardwood forests, grasslands, deserts, then tundra. Their numbers are reduced in highly developed or agriculturally developed areas.

Oribatid mites are a highly diverse order of mites, with varying numbers of species being found in different areas based on habitat, however there are well over 150 different species reported in some areas.

In addition to being one of the most abundant soil species, oribatid mites are an arboreal species as well, which was not discovered until recently (~20 years ago).

Biology

Oribatid mites are 0.2 to 1.5mm in size, brown or colorless, with high amounts of calcium in their shells, which is sequestered throuhg fungal feeding. They reproduce slowly compared to other types of mites, with a life cycle of about a year. Oribatid mites differ from other microarthropods by having a sclerotized exoskeleton, resembling the millipede.