House Dust Mite

The European house dust mite (Dermatophagoides pteronyssinus) and the American house dust mite (Dermatophagoides farinae) are two different species, but are not necessarily confined to Europe or North America; a third species Euroglyphus maynei also occurs widely.
Size
The body of a house dust mite is just visible against a dark background in normal light. A typical house dust mite measures 0.4 millimetres (0.016 in) in length and 0.25–0.32 millimetre (0.0098–0.013 in) in width. Both male and female adult house dust mites are creamy blue and have a rectangular shape. The body of the house dust mite also contains a striated cuticle. Like all acari, house dust mites have eight legs (except 3 pairs in the first instar).