Mites Injurious to Domestic Animals. 95 



infected early in their adult life, they may continue to fly and work 

 for a long time. A false impression of recovery from the disease may 

 thus be conveyed. The mite has been found in workers, drones, 

 and queens, but the young stages of the bee do not seem to 

 harbour it. It also occurs sometimes in apparently healthy bees, 

 but in these the disorder usually makes its appearance at a 

 later date. In some instances, however, the mite seems to 

 be present without causing the disease, and heavily infested bees 

 may be capable of flight. All stages of the life cycle of the parasite 

 are found in the tracheal tubes of the thorax and sometimes of the 



FIG. 78. 



Tracheal tube of honey bee infested with Acarapis woodi. 

 (Photo by the Rev. G. H. Hewison.) 



head, and apparently the mites are restricted to this part of the 

 respiratory system. Acarapis woodi is oviparous, the eggs being 

 of very large size, when compared with the mite itself, and bean- 

 or kidney-shaped. They are laid in the tracheal tubes of the host. 

 The mite emerges from the egg in the form of a six-legged larva 

 (fig. 82), which subsequently develops into the adult. Adult mites 

 of either sex are frequently to be met with fully-developed but still 

 enclosed in the larval skin. Apparently infection takes place through 

 the thoracic stigmatal openings. The mites, no doubt, set up ill 

 effects through blocking the tracheal tubes, and probably also 

 through sucking the blood of their host. It has been suggested 



