Trombicula species These parasites, also known as red bugs, are the larval forms of several closely related microscopic mites. Only the larvae are harmful. They hatch from eggs laid in the soil of uncultivated, scrubby woodland or marshy areas and attach themselves to people and other hosts as they pass by. Chiggers insert their mouthparts into the skin at the site of a pore or hair follicle, inject an enzyme that dissolves cell walls (and causes the itching), and feed on cellular fluid for several days until they become engorged and drop off.
To keep them out of the house, seal openings around doors and windows, inspect and repair screens. Clean up any debris outdoors that may harbor these pests.