AMERICAN FOULBROOD. 21 



larvae (PI. VI, D), about one- third of the larva being removed. The 

 transparency seen in healthy larvso disappears, and the bodies of the 

 ones affected become more nearly opaque. Soon the color assumes a 

 tint of brown which deepens as the process of decay continues, pass- 

 ing through chocolate, coffee, and mahogany shades. In the earliest 

 stages of the disease the body waU is ruptured more easily and the 

 tissues are softer than in healthy brood. As the disease advances 

 a ropiness of the decaying brood is to be observed, the characteristic 

 odor appears, and a loss in the strength of the colony is evident. After 

 a time an irregularity in the appearance of the brood comb is to be 

 seen, the capped and uncapped brood being abnormally distributed 

 with here and there perforated and sometimes sunken caps (PI. II, 

 A, B, C). Still later the scales are found. 



The time at which the various symptoms appear varies. Climatic 

 conditions, the amount of infection present, and the initial strength 

 of the colony are some of the more important factors causing the 

 variations. 



Whether a hive which has housed a colony infected with American 

 foulbrood wiU transmit the disease is a question which has not been 

 altogether solved but in experimental work all hives that have housed 

 such colonies should be disinfected before they are used again. This 

 can be done satisfactorily by flaming the inside of the hive. If 

 gas is available the Bunsen burner is very satisfactory for this purpose. 

 That no fear need be entertained from hives which have been flamed 

 properly is demonstrated by the fact that the disease has not been 

 transmitted by flamed hives in the experiments made in the present 

 studies, although the -number of such hives which have been used is 

 large. The length of time that a sirup or honey suspension of Ameri- 

 can foulbrood spores stands before the inoculation of a colony is 

 made need not be considered in experimental work. 



From what is known of American foulbrood its transmission by 

 queens is not to be expected. Two queens from diseased colonies 

 were introduced into healthy ones in October and the colonies were 

 kept under observation until the foUowing July. The disease did 

 not appear in either of them. In a number of instances during the 

 investigations queens from American foulbrood colonies were used 

 to queen nuclei made by division of healthy colonies. These colonies 

 were under observation for weeks or months before they were used 

 for American foulbrood experiments. In no instance was the disease 

 observed to result from the use of these queens. The conclusion is 

 reached, therefore, that for most experimental work at least the possi- 

 ble previous relation of the queen to diseased colonies need not concern 

 one. 



The combs from an American foulbrood colony never should be 

 given to a colony which is to be used for experimental purposes. 



