DIAGNOSING BEE DISEASES IN THE APIAEY 11 



pluton or other forms of bacteria, found iii larvae affected by Euro- 

 pean foulbrood, It seems probable, therefore, that B. alvei and 

 B. pluton are only different forms of the same bacterium. 



RACES OF BEES AFFECTED AND CONDITION OF COLONIES 



Common black and Italian-black hybrid bees are more frequently 

 affected by European foulbrood than are Italians, and weak colonies 

 are usually more seriously affected than are strong ones. This dis- 

 ease frequently appears year after year in colonies of black or hybrid 

 bees, and heavy losses may be suffered, but among: Italian bees 

 losses are usually unimportant. At times, however, European foul- 

 brood 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 

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

 fected. Sometimes this disease appears suddenly and spreads rapidly 

 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. 8, 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 

 brood, are irregularly scattered among cells of capped brood (fig. 9). 

 Cells with discolored, sunken, or punctured cappings (fig. 8, N and 

 O) may be present, but these are less common than in American foul- 

 brood. 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 LAEVAE ANI> 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. 8, A-I). Many larvae also die at the age when they 



