26 



BULLETIN 804, U. S. DEPAKTMENT OF AGRICULTURE 



importance probably, BacUhis pluton was found in a smear made 

 from the mouth parts of a nurse bee and also in the contents of the 

 honey stomach of another. If these observations had been carried out 

 systematically, instead of only casually, it is expected that much more 

 positive data might have been obtained along these lines, owing to 

 what is known already of the habits of house-cleaning bees working 

 on diseased material. 



Table IV. — The results of the microscopic bacterial examination of the contents 

 of the intestinal tracts of nurse tees taken from diseased colonies 



SUMMARY AND CONCLUSIONS 



In arriving at the following conclusions an effort has been made 

 to state them in a manner which will indicate the substantiation of 

 previous observations made both in the laboratory and in the apiary. 

 It may be noted that many of these conclusions are similar to some 

 of the statements made in Farmers' Bulletin 975 in the summary of 

 facts which apiary practice has brought out. 



1. European foulbrood is an infectious disease. BaciUvs plioton 

 was found to be the primary invader, appearing in the intestinal tract 

 of larvae before death, contemporary with the first slightly apparent 

 symptoms. 



2. The variation in the appearance of the diseased larvae after death 

 is due to the presence or absence of secondary invaders. 



3. The period of incubation for European foulbrood was found 

 to be from 36 to 48 hours, although the gross symptoms usually do not 

 become apparent in less than 3 or 4 days, varying with conditions 

 of honey flow and strength of colony. 



4. It has been noted in apiary practice that the first brood of the 

 year usually escapes with little loss. During the first 5 to 7 days the 

 spread of the disease in the colony after infection is slow, after which 

 the increase is rapid under favorable conditions. The critical time, 

 therefore, to detect the disease and start treatment is early in its 

 course, thus making conditions unfavorable. 



5. The evidence tends to confirm the theory that one of the ways 

 the disease is spread in the colony is by the house-cleaning bees, and 

 from colony to colony by their drifting. It is quite probable that the 

 infective organisms are carried on the mouth parts and pedal appen- 

 dages. The question of infection from intestinal contents or from 



