6 farmers' bulletin 975. 



position of the larva is one of the best means of differentiating 

 American foulbrood and European foulbrood. In American foul- 

 brood the larvae almost without exception are found on the lower 

 side wall, while in European foulbrood they may be there, or at the 

 base of the cell, or on any of the side walls, even the upper one. 



(4) Color. — As the decay proceeds the color changes to a decided 

 yellW or gray and the translucency is lost (fig. 1, Q, H) . When the 

 disease first appears in a region the yellow color of the decaying 

 larvae seems more constant than later, due probably to the fact that 

 as the disease spreads the germ causing the disease is accompanied 

 by other organisms. The yellow color may be taken as the chief 

 characteristic of the disease. The dead larva appears as a moist, 

 somewhat collapsed mass, giving the appearance of being melted. 



(5) Scale. — When the remains have become almost dry (fig. 1, C), 

 the tracheae sometimes become conspicuous again, this time by re- 

 taining their shape, while the rest of the body content dries around 

 them. Finally all that is left of the larva is a yellow or grayish- 

 brown scale against the base of the cell (fig. 1, F, H), or a shapeless 

 mass on one of the side walls if the larva did not retain its normal 

 position before death (fig. 1, N, O). Very few scales are black. 



(6) Adhesion to cell. — At no time during the decay does the larva 

 adhere to the wax closely, but is easily removed, and the bees carry 

 out a great many of them in their efforts to clean house. 



(7) Usual lack of ropiness. — A slight ropiness is sometimes ob- 

 served in the decaying larvae. This is not, however, at all like the 

 fine ropiness observed in larvae dead of American foulbrood, but the 

 decaying mass behaves more like an old rubber band which has lost 

 its elasticity and which breaks when stretched. 



(8) Odor. — ^There is usually little odor in European foulbrood, but 

 sometimes a sour odor is present which reminds one of yeast fermen- 

 tation. This odor is quite constant in some regions and seems to 

 come from the decay due to organisms other than the one which 

 causes European foulbrood. 



(9) Sex. — A symptom of the greatest importance is the fact that 

 the disease attacks drone and queen larvae ^ nearly as quickly as those 

 of the workers. 



(10) Epidemic cMracter. — In regions where the disease occurs a 

 considerably larger percentage of colonies is affected than is usual 

 for American foulbrood. However, not many colonies die of Euro- 

 pean foulbrood, but the chief trouble is that weakened colonies suc- 

 cumb during winter unless well cared for. The disease spreads at 



1 The tendency of this disease to attack queen larvse is a serious drawback in treat- 

 ment. Frequently the bees of a diseased colony attempt to supersede their queen, but 

 the larvoi In the queen cells often die, leaving the colony hopelessly queenless. ' The 

 colony Is thus depleted rapidly. 



