EUROPEAN FOULBROOD. 



11 



finally filling it more or less completely (PI. VII, J) . The growth does 

 not always take place uniformly along the peritrophic membrane (PI. 

 VII, J) , nor does it extend beyond it (PI. VII, I, J, K) , but is inclosed 

 withm the sac, the tissues of the larvae not being reached. The mul- 

 tiplication of the organism after the death of the host, if, indeed, it 

 takes place at all, is limited. 



Secondary invaders, chiefly Bacillus alvei, BacteHwm emydice, 

 Streptococcus apis, and occasionally Baaillus orpheus, and a few 

 others, are encountered at various stages of the disease and during the 

 decay of the lar\'a. During the life of the larva these species also 

 remain within the peritrophic sac. 



BACILLUS ALVEI 



Bacillus alvei (fig. 2; PL VII, D, F) is present very frequently and 

 in very large numbers in larvae dead of European foulbrood. The 

 species was well described by 

 Cheyne (4). Descriptions maybe 

 found elsewhere also (11, 13). It 

 is readily recognized and may be 

 differentiated easily from other 

 spore - producing species occa- 

 sionally encountered in the dis- 

 eased brood. 



Bacillus alvei is not the active 

 cause of any bee disease. It 

 seems probable, however, that it 

 plays a role in European foul- 

 brood, but the extent is not fully 

 known. The species is present 

 usually, if not invariably, in large 

 numbers in the rubber like scales (PI. V, F, I), which resemble 

 so much those of American foulbrood. The decayed larval mass, 

 which forms the scale, before becoming dry is ropy in consistency 

 similar to that of American foulbrood but to a less degree. It 

 seems probable that this ropiness is due more or less directly to 

 Bacillus alvei. On account of this viscidity the decaying mass, as 

 well as the scales, are removed with greater difficulty than ai'e most 

 larvae dead of European foulbrood. The result, as often observed, is 

 that these brown viscid decaying larvae or the rubberlike scales result- 

 ing from them are the only evidence that European foulbrood is 

 present in the colony. 



While Bacillus pluton in such larval masses and scales is often diffi- 

 cult to detect microscopically, its presence can be demonstrated 

 through the experimental inoculation of healthy larva. Inasmuch as 

 Bacillus pluton will live for a considerable period in the scales, it 



Fig. 2. — Baeillus alvei. Spores free from 

 and others within rods. 



