10 DISEASES OF BEES 



niunber of eggs succeeded in hatching, but that the larvae which 

 developed from them, a few of which were sealed over by the bees, 

 died before reaching maturity. This seems to have been a mixed 

 case of Addled eggs and Addled brood, the queen being responsible 

 for the condition. In 1925 Anderson described cases of Addled 

 brood in Scotland. These cases were marked by the fact that prac- 

 tically all the sealed brood died just prior to the time of emergence, 

 but occasionally addled eggs (eggs which did not hatch) were 

 noticed, and, of the bees which did succeed in developing, many 

 could not fly. The disease could be produced in healthy colonies 

 by introducing queens from affected stocks to them, while requeen- 

 ing affected stocks with normal queens always cleared up the 

 disease. Moreaux, working in France, has also recently described 

 a case of Addled brood. His paper appeared at about the same 

 time as the 1935 report on brood diseases was issued from this 

 Station. In the last named article the appearance of larvae in 

 cases of Addled brood (" Uncertain ") was described in some detail. 

 It appears that the numerous cases of diseased brood received at 

 this Station in which at tirst no accurate diagnosis could be made, 

 and which were temporarily designated " Uncertain," were, in 

 reality, cases of Addled brood. Unfortunately there is not time to 

 describe in detail the appearance of larvae dead of this disease. 

 Normally the pupae or prepupae are attacked, the appearance of 

 the dead brood being similar to that noticed in larvae which have 

 died and imdergone autolysis. Usually these larvae are almost, 

 or quite, sterile bacteriologically. The results of a series of experi- 

 ments which have been carried out in order to ascertain the cause 

 of the complaint leave no doubt that it is, in effect. Addled brood. 

 There is every indication that the complaint can vary greatly in 

 severity. Thus in some colonies relatively few Addled pupae are 

 seen, and such a colony may show few or no external symptoms of 

 weakness. On the other hand some stocks may be badly affected, 

 and become so weak that they store no surplus honey and may even 

 fail to resist the winter. It seems fairly certain that the cases 

 investigated by Anderson merely represented very severe Addled 

 brood in which very advanced pupae were those chiefly affected. 



In three years, fifty-eight samples of Addled brood have been 

 sent in, representing about 28 per cent, of all the samples received. 

 Preliminary experiments showed that the disease, unlike American 

 and Eiu^opean foul brood, is not contagious : combs containing an 

 abundance of affected pupae when placed in healthy nuclei never 

 caused disease. During the past season queens taken from affected 

 stocks have been obtained from certain beekeepers, and several 

 of these have been successfully introduced to queenless nuclei. 

 In every case in which such a queen was accepted, the nucleus 

 concerned soon showed signs of Addled brood ; a certain propor- 

 tion of the sealed brood produced by the queen, dying before 

 reaching maturity. When the affected queen was removed from 



