February, '16] mccray: brood disease diagnosis 195 



brood. The scales of these diseases, as you all know, are formed by 

 the drying of the affected larva?. The character of these scales is 

 usually so different that there is little danger of confusing one with the 

 other. The scales of American foulbrood are so characteristic that a 

 positive diagnosis of the disease in this stage can almost invariably be 

 made. Let it be distinctly understood that a number of scales, not a 

 single scale, is sufficient to make such positive diagnosis. It is not 

 uncommon to receive for diagnosis, specimens of comb with a single 

 affected larva, often in the form of a scale. Certainly no one should 

 presume to make a gross diagnosis from such meagre material. Yet 

 the same has been done and if the diagnosis was later confirmed by 

 finding other infected larva? in the colony, the original diagnosis should 

 be considered good luck rather than skill. A laboratory diagnosis even, 

 from a single larva, is frequently considered unsatisfactory by the 

 examiner. Specimens are often received for diagnosis containing less 

 than half a dozen scattered scales, or even a single scale of rubber-hke 

 consistency, which in coloration, position of being stretched out from 

 base to top along the lower cell wall, and even difficulty with 

 which it separates, all indicate scales of American foulbrood and no 

 doubt such scales have been diagnosed as belonging to this disease. 

 Closer examination, however, will usually reveal such scales to be of a 

 lighter shade of brown than the scales of American foulbrood and they 

 are not found in such great number in a given area of comb as American 

 foulbrood scales. The decided rubber-like quality exhibited on at- 

 tempting to break or draw out these scales, should put one on guard. 



Besides these large rubber-like scales of European foulbrood. there 

 is the much more common form described as being smaller than 

 American foulbrood scales, greyish-brownish or yellowish in color and 

 lying usually against the base of the cell. These small scales are not 

 nearly so characteristic of European foulbrood as are the scales de- 

 scribed for American foulbrood. Larvae dying from other causes 

 may bear quite a close resemblance to the small greyish, brown- 

 ish or yellowish scales of European foulbrood. The rubber-hke scales 

 of European foulbrood occur infrequently and in small numbers, 

 hence in a small piece of comb might be mistaken for scales of 

 American foulbrood. European foulbrood cannot be diagnosed in 

 the scale stage with the cei"tainty that American foulbrood can. In 

 fact, it is practically impossible to diagnose European foulbrood after 

 it has passed to the scale stage. 



Scales are sometimes found in specimens of sacbrood. These are 

 often quite dark, even black in coloration, sometimes vnth tint of grey, 

 especially the under surface in contact with the cell wall from which 

 they separate quite readily. The peculiar distended condition and 

 granular watery content of larvse affected with sacbrood should make 



