The entire mite life cycle is spent within the trachea or breathing tubes in the thorax of adult honey bees except for brief migratory periods. Mites are also occasionally found in air sacs in the thorax and abdomen. Within the trachea, the mite reproduces and feeds. Mites penetrate the breathing tube walls with their mouthparts and feed on blood. Normal thoracic tracheae are clear, colorless, or pale amber in color.
Infested tracheae deteriorate progressively and show patchy discoloration.
In a slight infestation, one or both tracheal tubes contain a few adult mites and eggs which can be detected near the spiracular openings. The tracheae of severely infested bees have brown blotches, with brown scar tissue, crustlike lesions, or they may appear completely black, and are obstructed by numerous mites in different stages of development, as well as mite debris. As a result of mite feeding, the blood of infested bees has a higher than normal bacterial count. Within 24 hours after worker bees emerge from their cells, female mites migrate into their trachea by passing through the first thoracic spiracle and remain there for life's duration or until their host dies. Each female mite lays 5 to 7 eggs within 3 or 4 days after entering the trachea and continues to lay eggs throughout her life.