AMERICAN FOULBROOD. 11 



of old brood comb. This mahogany-hued mass is viscid in consis- 

 tency, showing the ropiness that characterizes brood dead of American 

 foulbrood. 



FIFTH STAGE 



Finally after a few weeks of decay and drying there is to be found 

 in the cell the more or less dry residue of the dead pupa — the scale 

 (PL V, C, F; PI. VI, F, I). It covers most of the floor and some of the 

 side walls and only a portion of the bottom. The pupal scale is in 

 many respects similar to the larval scale. It is concave from side to 

 side. The ventral surface is slightly roughened by the dry decayed 

 appendages. The posterior third extends only slightly upon the 

 bottom of the cell. This can be demonstrated by cutting the scale 

 (PI. VI, I) lengthwise as it occupies its position in the cell. The 

 scale is dark brown resembling in shade that of old brood comb. It 

 adheres rather firmly to the cell but with care can be removed from 

 it. When thoroughly dry and removed it is found to be quite brittle. 



ETIOLOGY 



PREDISPOSING CAUSES 



Age. — American foulbrood infection takes place only during the 

 feeding stage of larvae. Death occurs almost invariably after the 

 feeding stage is passed, i. e., after capping, and either while in the 

 larval stage or soon after transformation to the pupa. Older pupae 

 do not die as a result of the disease and adult bees do not become 

 infected. 



Sex. — That worker, drone, and queen larvae are all susceptible to 

 the disease has been demonstrated during these studies. Affected 

 drone brood is encountered less often in the diagnosis of this disease 

 than in that of European foulbrood. The writer has encountered 

 queen larvae affected by American foulbrood in experimental colonies 

 only, although very probably diseased queen larvae do occur in 

 nature also. 



Race. — Thus far no race of bees has been shown to possess com- 

 plete immunity from the disease. In the experimental inoculations 

 recorded in the present paper bees mixed with Italian blood were 

 used for the most part. The queens in many of the colonies were 

 purchased as " untested Italians." At least five colonies of " tested 

 Italians," two of " tested Carniolans," and two "tested Caucasians" 

 were inoculated. Among the colonies used there were also several 

 common black bees. The disease was readily produced in all of these 

 strains. Furthermore, the results obtained from the examination of 

 numerous samples of diseased brood received from beekeepers through- 

 out the United States indicate that all strains of bees commonly 

 found in American apiaries are susceptible to infection with American 

 foulbrood. No definite conclusion can be drawn at the present time 

 regarding the relative immunity possessed by the different races. 



