AMERICAN FOULBROOD. 37 



made from the symptoms (p. 5) alone. No helpful sign is found in 

 the appearance of the adult bees. A weak colony justifies a suspi- 

 cion that a disease is present. In American foulbrood, as in Euro- 

 pean foulbrood and sacbrood, a sample suitable for diagnosis must 

 contain the remains of brood dead of the disease. 



The colony symptoms which are usually adequate for a definite 

 diagnosis of American foulbrood are the following: The death of 

 larvae in capped cells after the endwise position has been assumed 

 (Pis. I, 11,111, VI), and the death of pupae soon after transformation 

 (Pis. IV, V, VI), the brown shade of dead brood, the viscidity (ro- 

 piness) of the decaying remains, the character of the scales, and the 

 foulbrood odor. 



BACTERIOLOGICAL EXAMINATION 



A conclusive diagnosis of American foulbrood can always be made 

 from a bacteriological examination of brood dead of the disease. 

 With gross characters suggesting the disease the experienced can 

 frequently make the tentative diagnosis definite by a water mount 

 made from the decaying brood remains, or the scales. A very large 

 nimiber of spores free from rods with no other bacterial species 

 present is the characteristic microscopic picture in the disease. The 

 spores are those of Bacillus larvae (fig. 4; PI. VII, B, D). As a rule, 

 a stained preparation does not furnish much additional aid. In all 

 cases of doubt cultures (agar plates are satisfactory) should be made. 

 The absence of growth on the plates when the other data strongly 

 suggest American foulbrood is sufficient for a positive diagnosis. In 

 routine work the cultures should always be made. Occasionally 

 further evidence that the spores present are those of B. larvae is 

 desired. This can be obtained by the employment of methods and 

 media given in this paper (p. 17). 



DIFFERENTIAL DIAGNOSIS 



EUROPEAN FOULBROOD 



European foulbrood can be recognized (27) in most instances by 

 the death of brood in uncapped cells, the yeUow hue of larvae recently 

 dead changing later often to a brown, and an absence of the foulbrood 

 odor. In cases in which these younger larvae have been removed, the 

 diagnosis of European foulbrood can very often be made from the 

 remains of brood which has died in capped cells. In these cases 

 the remains of dead larvae and not of pupae are encountered. These 

 decaying masses pass through a stage at which they are somewhat 

 viscid. The scales are rubberhke ^ in consistency. In these masses 

 and in the scales large numbers of B. alvei are found. 



1 The term "rubberlike" needs interpretation. When applied to the scales of European foulbrood it 

 means simply that they are less brittle than either those of American foulbrood or sacbrood. The property 

 "elasticity" as usually thought of in common parlance in connection with rubber is not meant. 



