932 MICROBIAL DISEASES OF INSECTS 



of disease in these larvae. In 1892 an editorial in one of the bee jour- 

 nals stated that dead brood had been encountered which did not seem 

 to be infectious and which lacked two decisive symptoms of the real 

 foul brood, i.e., the ropiness and the " glue-pot" odor. In 1902 

 G. F. White of the U. S. Dept. of Agriculture began the study of this 

 diseased brood. This disease was described in Switzerland in 1906 

 and later in 1910. It occurs among bees in localities having as wide a 

 range of climatic conditions at least, as are found in the United States. 



The name "sac brood" comes from the fact that many larvae dead 

 of this disease can be removed from the cell without rupturing their 

 body wall. When thus removed they have the appearance of a small 

 enclosed sac. 



SYMPTOMS. The strength of a colony in which sac brood is present 

 is frequently not noticeably diminished. When the brood is badly in- 

 fected, however, the colony naturally becomes appreciably weakened 

 thereby. The death of the worker larvae is the primary cause for the 

 weakness resulting from the disease in a colony. The colony is also 

 weakened by the dead sacbrood larvae remaining in the cells for weeks as 

 they not infrequently do, thus reducing the capacity of the brood nest 

 for brood rearing. The brood dies after the time of capping. The dead 

 larvae are, therefore, almost always found extended lengthwise in the cell 

 and lying with the dorsal side against the lower wall. It is not unusual 

 to find many larvae dead of this disease in uncapped cells. Such brood, 

 however, had been uncapped by the bees after it died. In this disease 

 the cappings are frequently punctured by the bees. Occasionally a 

 capping has a hole through it, indicating that the capping itself had 

 never been completed. A larva dead of this disease loses its normal 

 color and assumes at first a slightly yellowish tint. "Brown" is the 

 most characteristic appearance assumed by the larva during its decay. 

 Various shades are observed. The term "gray" might sometimes 

 appropriately be used to designate it. The form of the larva dead of 

 this disease changes much less than it does in foul brood. The body 

 wall is not easily broken, as a rule. On this account, often the entire 

 larva can be removed from the cell intact. The content of this saclike 

 larva is more or less watery. The head end is usually turned markedly 

 upward. The dried larva or scale is easily removed from the lower 

 side wall. There is practically no odor to the brood combs. Adult 

 bees are not susceptible to the disease. 



