I found a dead honeybee at the end of the summer that on further inspection appeared to have small "scab-like" structures all over its body. The view of a hind leg below shows these structures under low power through a light microscope. On examining them with a Scanning Electron Microscope it is possible that they are Tracheal mites. The body size is right and it is possible they left the body of the bee for a more promising host. These Mites clog the trachea of bees and damage the tracheal walls. This permits a wide range of other bee infections.

 

Reference

Disease: Honey Bee Parasites, Pests, Predators and Diseases - Department of Entomology, Penn State University

Tracheal Mites : Honey Bee Tracheal Mites - Acarapis woodi