18 



CIRCULAR 3 92, U. S. DEPARTMENT OF AGRICULTURE 



soon changes to a brown or grayish brown and later a dark brown. 

 Scales are almost black for the entire length, the head end usually 

 being darkest. 



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 BEOOD 



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 



Figure 7. — Sacbrood: A, Oral view of healthy larva at the age when death usually 

 occurs from sacbrood; B—F, stages in decay and drying of larvae dead of sacbrood. 



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

 skin becomes wrinkled, usually most noticeable in the front third 

 (fig. 7, G-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. 8, G) . In contrast 

 with American foulbrood (fig. 3, G) , the head and front third of a 

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

 gresses, 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. 



