20 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE, 1944 
which is used for thinning fruit, indicate that (hey may hecome a 
menace both to pollination and to beekeeping. Neither of the.-e ma- 
terials was repellent to bees. A 0.05-percent concentration of DDT 
fed in syrup to honeybees acted as a stomach poison. Contact with 
a 10-percent DDT dust proved fatal to bees. Bees in contact with 
a surface sprayed with a 2-percent solution of DDT died within 6 
hours. When brood and adult bees were sprayed with a 0.05-penent 
solution of DDT. the unsealed brood was killed within a few hours 
but the sealed brood and adults were unaffected. 
All bees fed a 0.125-percent solution of dinitro-o-cresol in sugar 
syrup were dead within 24 hours. A 1.25-percent solution was neither 
repellent to bees nor effective as a contact poison. 
HONEY YIELDS INCREASED BY SUPERIOR STOC K 
Uniform testing methods were employed to compare the honey- 
producing capabilities of 9 lines of stock. In these tests 125 package- 
bee colonies which produced a total of. 14.200 pounds of honey were 
used. The highest yielding colony, in spite of a poor to mediocre sea- 
son, produced 250 pounds and the lowest 19 pounds. The average per- 
colony yield of the best line was 160 pounds, that of the poorest 52 
pounds. The high-producing line was characterized by a narrow 
spread between the yields of the best and poorest colonies. 
These tests indicate the need to develop superior lines of stock as a 
means not only of increasing profits in beekeeping but of improving 
pollination. 
ADVANCES IN ARTIFICIAL INSEMINATION OF QUEEN BEES 
Heretofore it has not been possible to use artificially inseminated 
queen bees in studies of practical beekeeping problems. Excessive 
losses of queens caused by long delays in the initiation of egg laying, 
as well as the abnormally short egg-laying period of inseminated 
queens, has precluded their use in field tests on honey production, 
resistance to disease, and other problems. By resorting to multiple 
inseminations, however, queens with the fecundity of naturally mated 
queens are now possible. The average number of sperms in drones 
ranged from 5.1 to 9.9 million, according to their age. In naturally 
mated queens the average sperm count was 5.7 million. Sperm counts 
from queens after one artificial insemination ranged from 2 to 3 mil- 
lion. An average of 5 million sperms per queen was obtained by using 
several drones. Multiple inseminations also advance the initiation 
of egg laying. Multiple-inseminated queens equaled or bettered natu- 
rally mated queens in egg-laying performance. 
NEW TECHNIQUE FACILITATES WORK ON KKSISTANTE TO DISEASE 
Gradual increase in resistance to American foulbrood has been ob- 
tained through the generation with naturally mated' queens. How- 
ever, in the seventh and eighth generations, although resistance was 
maintained, it was not improved. Queens of the I\, and F 7 genera- 
tions artificially Inseminated showed marked increase in resistance 
over the naturally mated ones. 
