BULLETIN 671, U. S. DEPARTMENT OF AGRICULTURE. 



MICROSCOPIC EXAMINATION. 



The number of larvae or pupae to be examined in a given sample 

 depends upon various factors. If the case is a typical one, one larva 

 or pupa dead of a disease usually is sufficient. If, on the other hand, 

 the gross appearance is not so definite and the microscopic picture 

 from the first dead remains examined is unsatisfactory, others must 

 be studied. "While much might be written concerning the microscopic 

 appearance of smears from larvae or pupae affected with the various 

 brood diseases, as compared each with the others and with smears 

 from healthy brood, such elaborate descriptions are not deemed ad- 

 visable in this paper. Only the more salient features of the micro- 

 scopic picture will be given for each disease considered, as it is 

 believed that such descriptions will best serve those for whose benefit 

 the paper is prepared. 



It will be understood that when the authors write of the recog- 

 nition of certain organisms by microscopic examination, as, for 

 example, that of Bacillus pluton or Bacillus alvei, either in stained 

 smears made from tissue or in stained smears made from agar plates, 

 they refer to the recognition of the organism under observation only 

 in a general way, meaning rather that the microscopic picture sug- 

 gests the organism. The identification of the organism is complete, 

 naturally, only after a consideration of its cultural characteristics 

 also. 



CULTURES. 



In culturing the affected brood agar as ordinarily prepared in the 

 laboratory is used in making plates. Those larvae or pupae are 

 selected which upon microscopic examination have shown evidence 

 of disease. Of course as many additional ones may be cultured as 

 desired. The cultures are incubated for different periods of time, as 

 will be noted in the discussion of the diseases. 



Dead, not living, larvce are examined. — In the laboratory examina- 

 tion of diseased bee brood, the affected larvae are always received 

 dead, therefore nothing will be said relative to symptoms and appear- 

 ance of affected living larvae. 



DISEASES TO BE DIAGNOSED. 



EUROPEAN FOULBROOD. 



European foulbrood is an infectious disease of the brood of bees 

 caused by Bacillus pluton (White, 1912). 



GROSS CHARACTERS. 



(a) The caps and regularity of the orood. — Larvae that die of 

 European foulbrood do so usually before they reach the age at 

 which brood is capped. Brood dead of the disease is therefore usu- 

 ally found in uncapped cells. When the larvae die after capping 



