dust mite

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of several mites of the family Pyroglyphidae, especially Dermatophagoides pteronyssinus and D. farinae, that feed on shed skin cells and produce excrement that is a common household allergen associated especially with asthma and respiratory allergies.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A microscopically small mite, of the Dermatophagoides pteronyssinus, or Dermatophagoides farinae species.