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 tubes with their mouthparts and feed on blood. Normal thoracic tracheae are clear, colorless, or pale amber.
Infested tracheae deteriorate progressively and show patchy discoloration.
At this stage, the tracheae may appear clear, cloudy, or slightly discolored. The tracheae of severely infested bees have brown blotches, with brown scabs or crustlike lesions, or they may appear completely black, and are obstructed by numerous mites in different stages of development, as well as mite debris. Trachea that are normally elastic and flexible become stiff and brittle. Discoloration and atrophy of flight muscles may also occur. As a result of mite feeding, the blood of infested bees has a higher than normal bacterial count.