934 MICROBIAL DISEASES OF INSECTS 



may be produced at any season of the year that brood is being reared. 

 Under natural conditions, however, the disease is more often encountered 

 during the first half of the brood-rearing season than during the second 

 half. The course of the disease is not greatly affected by the character 

 or quality of the food obtained and used by the bees. 



Bees have a tendency to remove diseased or dead larvae from the cells. 

 When the removal is attempted about the time of death it is done 

 piece-meal. Just what becomes of these bits of diseased tissue, is not 

 known. If these fragments were fed to young healthy larvae within a 

 week, they would most likely become infected with sacbrood. Exper- 

 ience, however, shows that under these conditions the tendency in a 

 colony is in most cases toward recovery. This suggests that the 

 workers may feed the infected tissues to the older larvae or to adult bees; 

 in either case the likelihood of the transmission of the disease would 

 apparently be very materially reduced. If the infective material 

 were stored with the honey and did not reach the brood in a month or 

 six weeks, again it is not probable that the disease would be transmitted. 



If the infective material is removed from the hive and freed from 

 the adult bees removing it, experimental evidence indicates that during 

 the warmer seasons at least, there is but little chance of the virus being 

 returned to the hive and producing any noticeable infection. 



There is also little probability of the virus of sacbrood being trans- 

 mitted by way of flowers visited by bees. There is, however, a greater 

 likelihood of the water supply being a source of infection. 



Bees drifting or straying from infected colonies to healthy ones have 

 been proved to be less liable to transmit the disease than when robbing 

 occurs. It is not yet known in what way the sacbrood virus is carried 

 over from one brood rearing season to another. 



From knowledge obtained through experimentation but few control 

 measures can be advocated. Most of the advice which can be given is 

 negative. Theoretically it is better to store combs from sacbrood col- 

 onies for one or two months before they are again used, as drying ap- 

 parently destroys the virulence of the virus within this time. After 

 the early brood-rearing season of the year is past brood frames from 

 badly-infected colonies may be inserted into strong, healthy ones, and 

 cause thereby very little infection and consequently only a slight loss. 

 This is the preferable method of disposing of the infected combs for the 

 practical beekeeper to employ. In practical apiculture no fear need be 



