20 CIRCULAR 3 9 2, U. S. DEPARTMENT OF AGRICULTURE 



There is little, if any, distinctive odor associated with sacbrood, 

 although watery, saclike larvae in the later stages may have a 

 slightly sour odor. 



CONSISTENCY OF DEAD BROOD 



The skins of dead larvae remain tough, and are easily removed 

 from the cells intact. The internal tissues at the same time become 

 watery, but rarely show any indication of ropiness. Suspended in 

 the waterlike liquid are numerous fine brown granules. When a 

 dead larva is removed from the cell, liquid collects beneath the skin, 

 which resembles a sac ; hence the name sacbrood. As the larva dries, 

 the skin becomes wrinkled, usually most noticeable in the front 

 third (fig. 13, C-F). After thorough drying it forms a scale. 



POSITION OF THE DEAD BROOD IN THE CELLS 



Larvae killed by sacbrood almost invariably lie extended length- 

 wise with their backs on the floor of the cells (fig. 14, G). In con- 

 trast with American foulbrood (fig. 5, G), the head and front third 

 of a larva dead of sacbrood is elevated while the tail end, as drying 

 progresses, slumps partly down off the bottom of the cell. The 

 raised head is a distinctive symptom of sacbrood. Since adult bees 

 often remove recently dead larvae by biting off a piece at a time, 

 occasional cells will be found in which only part of the dead larva 

 remains. 



THE SCALES 



Scales of larvae dead from sacbrood can be removed from the cells 

 with ease. They are dark grayish brown, or nearly black, and are 

 hard and brittle with the head end turned sharply upward. The 

 outline may be somewhat wavy. The back or lower surface is smooth 

 and polished, while the upper surface is rough and somewhat con- 

 cave. The lower surface takes the form of the cell walls and gives 

 the entire scale a boatlike appearance often referred to as gondola- 

 shaped or like a Chinese shoe. 



INFECTION WITH TWO OR MORE BROOD DISEASES 



In localities where two or more brood diseases are prevalent, more 

 than one brood disease will occasionally be found in the same colony 

 or even in the same comb. So far as is known a single larva is 

 never affected by more than one disease. When American foulbrood 

 is found in the salne comb with European foulbrood or sacbrood, 

 usually one of the diseases will be more prominent, at least in the 

 active stages, which may cause the mixed infection to be overlooked, 

 the beekeeper seeing only the most prominent symptoms. In cases 

 where there is doubt or a suspicion that more than one disease may 

 be present in the same colony, a laboratory diagnosis is desirable to 

 prevent improper treatment. Since American foulbrood is the most 

 serious, a careful search for this disease should always be made even 

 when another disease is known to be present. 



Table 1 gives in summary form the characters differentiating the 

 principal brood diseases. 



