Dust mites are microscopic animals related to other mites, and ticks, in the class Arachnida, which also includes spiders, scorpions, harvestmen (daddy-longlegs), and similar eight-legged creatures. Classification of mites is always changing, but dust mites are currently placed in the order Astigmata, family Pyroglyphidae, and genus Dermatophagoides(translates to “skin-eater”). The two most common species are:
North American house dust mite, Dermatophagoides farinae
European house dust mite, Dermatophagoides pteronyssinus
They both occur where human beings live, and where the humidity is optimal for their life cycle. Dust mites are known for causing allergies in millions of Americans and are treated by special mattress covers for dust mites.
Mites in general can be distinguished from insects by a lack of wings and antennae, and by having eight legs (though larval mites may have only six legs).
Mites can be separated from spiders by the fact that mites have only one recognizable body segment, as opposed to the two body regions spiders have.
One of the barriers to the identification of house dust mites is their literal invisibility. Even the adult mites cannot be detected with the naked eye. They measure a mere 1/100th of an inch, or:
one-fourth to one-third of a millimeter
The larvae and nymphs are even smaller. It takes a powerful microscope to see them, something the average person does not have ready access to.
What dust mites lack in size they make up for in sheer numbers. Densities of dust mites in the typical used mattress can range from 100,000 to ten million individual mites.
House dust mites feed and grow almost exclusively on the dead, shed skin cells that we humans shed daily by the hundreds of thousands.
While your bed is the chief place the majority of house dust mites reside, the mites can also survive in pillows, overstuffed furniture, even rugs and carpeting. The place where your pet sleeps is also a hot spot. Fido and Fluffy shed skin cells (dander), too.