14 



BULLETIN 804, U. S. DEPARTMENT OF AGRICULTURE 



cleaning until the colony was united with colony I, a slightly dis- 

 eased Italian colony. They then began cleaning the H combs, and 

 the combined colony was reported clean in August. 



COLONY A 



Race. — Italian with some possible slight hybrid blood. 



Queen. — 1918. Of their own raising. 



Bees.— Workers, good color; fairly quiet. Drones, some slightly darker 

 than pure Italians. 



Condition of eolmiy at time of infection. — ^Brood in seven frames about 

 half sealed. Bees covering about nine frames with a good proportion 

 of young nurse bees. Colony strong and building up. 



Date of first infection. — July 2, 1918. Second infection, July 6, 1918. 



Material used. — First, 20 diseased larvae from sample No. 5937 macer- 

 ated in 250 c. c. of a 50 per cent sirup, colored with eosin, ab- 

 normally heavy infection ; second infection, 20 diseased larvae from 

 sample No. 5953 in 250 c. c. of uncolored sirup. 



First appearance of disease noted. — July 8, 1918, in drone brood, six days 

 after infection. 



Age of larvce first attacked. — Four days after hatching from the egg. 



Colony A (fig. 5) was a fairly strong colony of Italians. Like col- 

 ony H, it was infected after the heavy honey flow had started and was 



Fig. 5. — The course of European foulbrood in colony A. 



given twice the amount of infective material colonies F and G received. 

 Nothing having appeared on the fourth day, a second infection of 

 the same amount was given. On the sixth day 6 diseased larvae 

 were seen in three combs. This colony, however, was" so strong that 

 the disease obtained very little foothold, and from the fourteenth 

 day began to decline, or at least failed to make further gains. As 

 a side experiment in this colony a comb of eggs laid by an Italian 

 queen was placed in between two combs showing disease. If there 

 is anything in the belief that Italian stock is more resistant to disease, 

 the larvae in this comb should not have developed the disease, or at 

 least not so soon. However, on the sixth day one or two larvae showed 

 disease, increasing slightly in numbers for a few days until the obser- 

 vations were of necessity stopped. It was intended to perform this 

 experiment with several variations, such as placing eggs laid by an 

 Italian queen in a diseased hybrid colony and placing eggs from 



