EPOW - Ecology Picture of the Week

Explanation:   In the photo above, you are peering down a microscope at 60x at a Pergamasus mite, a tiny predator of forest leaf litter and soil.  This specimen came from my Old Forest Remnants Study from northeast of Mt. St. Helens in the Cascade Mountains of southern Washington state.  

Smaller than the space in this letter "o" (rarely longer than 1 mm), this gamasid mite is a dominant soil predator and may play a major ecological role in soil food webs by controlling populations of other soil organisms.  Other members of this family are parasitic on birds, bats, small mammals, snakes, insects, and rarely humans.  

Mites are not insects (of Class Insecta), but rather share their taxonomy with ticks and spiders (Class Arachnida).  Like spiders, gamasid mites inject digestive fluids into their prey and then suction the dissolved tissues.  They are one of what E.O. Wilson called "the little things that run the world."  

Think they're rare?  Soil mites can number several  hundred thousand per square meter of soil.  

Populations and communities of gamasid mites tend to reflect availability of their prey, which are tiny arthropods that, in turn, also perform various key ecological functions of chewing, decomposition, and herbivory in soil ecosystems.  Thus, some genera of gamasid mites may be useful as bioindicators of habitat, soil condition, and the trophic health and structure of soil food webs.  

I took the following photos of gamasid soil mites at 200x (click for larger images):

The next photo clearly shows the opisthonotal shield which is the hirsute posterior portion of its dorsal exoskeleton (its "hairy back").

Acknowledgment:  Thanks to Dr. Andy Moldenke, Entomologist, Department of Botany, Oregon State University, for the identification