Dust mites. Coloured scanning electron micrograph (SEM) of house dust mites (Dermatophagoides pteronyssinus). Millions of dust mites inhabit the home, feeding on shed skin cells. They mainly live in furniture, and are usually harmless. However, their excrement and dead bodies may cause allergic reactions in susceptible people. The dust mite life cycle from egg to adult takes approximately one month to complete, mature female mites can lay from 1-2 eggs per day. Adult mites can live up to two months. Magnification: x60 when printed at 10 centimetres wide.