1920 



AMERICAN BEE JOURNAL 



227 



served, the likelihood of robbing, 

 swarming, absconding and accidental 

 straying or drifting of bees is re- 

 duced. 



In making the inoculations two 

 methods were used. Those have been 

 referred to as the direct and the in- 

 direct methods, respectively. Follow- 

 ing the direct method, a group of 

 about 10 to 20 larva;, 2 to 3 days old, 

 are fed thin sugar syrup to which has 

 been added the contents of stomachs 

 of sick larvse. This is done by put- 

 ting a very small quantity of the con- 

 taminated syrup directly with the 

 food of the larva within the cell. For 

 this purpose a small glass tube is used 

 Care must be taken that too much 

 syrup is not added in making 

 the inoculations, as the larvae 

 would be floated thereby. Care 

 must be observed also that they are 

 not disturbed mechanically by the 

 tube. Disturbances of this kind are 

 very likely to be followed by their re- 

 moval by the adult bees. Within 3 

 days the inoculated larvae show 

 marked symptoms of the disease, 

 some of the sick or dead ones are re- 

 moved by the end of the third day 

 and most of them before the end of 

 the fourth day. Only a few are found 

 infected outside the arena of brood 

 inoculated. The colony usually 

 speedily recovers from the infection 

 and no further evidence of the dis- 

 ease is seen. 



By the indirect method the entire 

 colony is inoculated through feeding 

 it about one-third of a pint of sugar 

 syrup to which the crushed bodies of 

 from S to 10 larvae sick or dead of the 

 disease have been added. The first 

 symptoms of the disease are ob- 

 served about 3 days after inoculation. 

 The youngest larvae to show symp- 

 toms are about 4 days old. After a 

 single feeding the colony usually 

 soon recovers from the disease. Other 

 factors being equal, the recovery is 

 more rapid when the amount of 

 brood is small in proportion to the 

 strength of the colony, when the flow 

 of nectar is good, and when the bees 

 are active. 



A stock of fresh disease material is 

 needed during most of the experi- 

 mental studies, and this can be se- 

 cured from colonies inoculated for 

 this purpose. In inoculating these 

 stock colonies the disease material 

 for the first feeding is taken from 

 samples received from the beekeep- 

 ers. Repeated inoculations are need- 

 ed, as a rule, to keep the colony dis- 

 eased, as there is a marked tendency 

 for the colony to recover from the in- 

 fection. The material for these sub- 

 sequent inoculations is taken from 

 the stock colonies themselves. For 

 the first inoculation the direct meth- 

 od is used, and for the subsequent 

 ones the indirect method is em- 

 ployed. 



It is only after repeated inocula- 

 tions have been made and the disease 

 has been in the colony for some time 

 that the rubberlike scales (Fig. 5. R, 

 T) are found that resemble in many 

 ways those of American foulbrood. 

 As these scales are somewhat diffi- 

 cult for the bee to remove, the num- 

 ber present naturally increases to a 



certain extent during the course of 

 the disease. The number encoun- 

 tered in any given area of brood- 

 comb, however, is always small. The 

 bees allow some of them to remain in 

 the brood-comb for a considerable 

 period. 



Some of the experimental colonies 

 that were rather heavily infected, 

 but which remained sufficiently 

 strong to winter well, were found to 



be diseased in the spring, but some 

 were not. Those that were only 

 lightly infected, as a rule, did not 

 show the disease the next year. 

 Whether the germs used had previ- 

 ously been in a diseased colony has 

 given the writer no uneasiness. All 

 hives which had housed a European 

 foulbrood colony were flamed inside 

 before they were used again. 

 (To be Continued) 



J -W O 



Fig. 5. European foulbrood. A to M uncapped, and N to T capped brood; D. healthy larva at 

 the earliest age at which symptoms of the disease appears; A E, young larvx showing symp- 

 toms of European foulbrood: B O, larv*e partially removed by tlie adult bees; C, scales from 

 young larva; F I, healthy larvae somewhat older than D. G H J, dead larvae of the same 

 age as F and I; K, healthy larvx slightly older than F. with dorsal side turned toward the 

 observer; L M, dead larv,i; about the same age as K; N, larva dead at the time of spinning: 

 O, scale of a larva similar to N; P, a punctured cap; Q R S T, larva which had assumed 

 the endwise position in the cell before death; Q. larva partially removed; S. lari'a dead of 

 the disease; R T, end and ventral view, respectively, of European foulbrood scales of larva of 

 the age shown in S. These scales and those of American foulbrood are quite alike. The 

 caps from N O Q R S and T were removed by the adult bees. 



