DIAGNOSING BEE DISEASES IN THE APIARY 11 



affected with European foulbrood. Thus it may be that B. pluton is 

 only a different form of B. alvei or B. eurydice, but until such cultures 

 are shown to produce European foulbrood by artificial inoculation 

 of healthy colonies, judgment must be withheld. 



RACES OF BEES AFFECTED AND CONDITION OF COLONIES 



Common black and Italian-black hybrid bees are more frequently 

 affected by European foulbrood than are Italian bees, and weak 

 colonies are usually more seriously affected than are strong ones. This 

 disease frequently appears year after year in colonies of black or hy- 

 brid bees, and losses may be heavy, but among Italian bees losses are 

 usually unimportant. At times, however, European foulbrood spreads 

 within strong colonies as well as within weak ones, and occasionally 

 Italian bees are seriously affected. 



EFFECT UPON THE COLONY 



European foulbrood is most common in the spring, when brood 

 rearing is at its height. Usually the earliest reared brood is not af- 

 fected. Sometimes this disease appears suddenly and spreads rapidty 

 within infected colonies. At other times it spreads slowly and does 

 little damage. As a rule it subsides by midsummer, but occasionally 

 it continues to be active during summer and fall, or it may reappear in 

 the fall. A good honey flow seems to hasten recovery. In severe 

 cases colonies are seriously weakened or killed. Usually the worker 

 bees remove dead brood promptly (fig. 5, M) ; but in some colonies, 

 particularly weak ones, it is allowed to accumulate. 



SYMPTOMS 



APPEARANCE OF THE COMBS 



In mild cases and in early stages of European foulbrood the ar- 

 rangement of the brood in the combs is not noticeably irregular. 

 The degree of irregularity increases with severity of the disease and 

 the length of time it has been present. In advanced cases open cells, 

 which may be empty or contain eggs or healthy or affected broods, 

 are irregularly scattered among cells of capped brood. Cells with dis- 

 colored, sunken, or punctured cappings (fig. 5, N and 0) may be 

 present, but these are less common than in American foulbrood. 

 Irregular arrangement of the brood is not a dependable symptom of 

 European foulbrood, however, and final diagnosis should depend upon 

 symptoms shown by the dead individuals. 



APPEARANCE OF SICK LARVAE AND TIME OF DEATH 



Sick larvae lose the plumpness and glistening white color of healthy 

 larvae and become flat white. A faint yellow color, which is an im- 

 portant symptom, may also appear before death. Sick larvae may 

 show abnormal movements and occupy an unnatural position in the 

 cells. 



The greater number of larvae die while coiled on the bottom of open 

 cells (fig. 5, A-I). Many larvae also die at the age when they would 



