What microscopic bug lives in dust?

Dust mites

PC: Bedbugs (or bed bugs) are small, elusive, and parasitic insects of the family Cimicidae. They live strictly by feeding on the blood of humans and other warmblooded animals. The name 'bed bug' is derived from the insect's preferred habitat infesting houses and especially beds or other common areas where people may sleep.[1] Bedbugs, though not strictly nocturnal, are mainly active at night and are capable of feeding unnoticed on their hosts.

Largely eradicated as pests in the United States in the early 1940s, bedbugs have been resurgent in the past decade to near epidemic proportions.