﻿EFFECTS ON HONEYBEES OF SPKAYING FEUIT TREES 23 



MINIMUM AMOUNT OF ARSENIC FATAL TO BEES IN CONFINE- 

 MENT 



. Chemical analyses of the samples of dead bees collected in 1914 at 

 Winchester and Winthrop, after fruit trees had been sprayed in 

 full^ bloom, showed that some samples taken at Winchester contained 

 0.0002 milligram of arsenic (As) per bee, and that some taken at 

 Winthrop contained as much as 0.0004 milligram per bee. It was 

 yet to be shown whether these quantities were fatal to bees. A series 

 of experiments intended to decide this question was conducted at the 

 bee culture laboratory at Drummond in July, August, and Septem- 

 ber of that year. 



METHODS 



To determine the behavior and to time accurately the longevity 

 of bees fed definite quantities of arsenicals in confinement, 11 tri- 

 angular observation cages were used, each made of 3 narrow wooden 

 strips 1 inch wide, 2 of which were 10 and the third 6 inches long. 

 Wire screen was used for the bottoms and tops of the cages, which 

 lay on a table by a window. Fifty workers from alighting-boards 

 were placed in each cage and fed definite quantities of poisoned 

 candy or honey in small feeders, one to each cage, so covered with 

 wire that the bees could not waste the food. 



As an illustration of the method of procedure, 20 grams of finely 

 pulverized confectioner's sugar and 1 milligram of finely pulverized 

 Paris green were thoroughly mixed together; 20 grams of honey 

 were added and the mixture again stirred thoroughly. The cages 

 and feeders were carefully washed and dried to be sure that they 

 were free of arsenic. One-tenth of this poisoned paste candy was 

 put in each of 10 feeders, and nonpoisoned candy in the eleventh, 

 for the control bees; in each cage were placed the 50 workers, and 

 lastly the feeder containing the food, poisoned or otherwise. In a 

 similar manner definite quantities of other arsenicals were thor- 

 oiighh^ mixed Avith definite quantities of honey- After the bees 

 had eaten all the poisoned food, great care was taken to see that they 

 had plenty of nonpoisoned food. Bees soon die in such cages when 

 deprived of food. The dead bees were counted and removed daily, 

 and samples, each of 25 bees, were prepared for analysis. The 

 results obtained ai-e only comparative and are based on the average 

 time required to kill all the bees tested, rather than on the absolute 

 single lethal doses required to kill them. It was assumed that the 

 bees ate ecjual quantities of the poisons, although this may never 

 have been true; but even if bees do not eat equal quantities of the 

 food given to them they have the habit of feeding one another, and 

 consequently may on this account digest approximately equal quan- 

 tities of food. In order to i-echice the probable errors to a minimum, 

 a large number of Ijees were used for each individual experiment. 



EXPERIMENTS AND RESULTS 



After the manner described in the preceding paragraph, 1 milli- 

 gram of Paris green was fed to 500 bees; assuming that they shared 

 it ('(fually, (!acl) bee ate 0.0008 milligram of arsenic. These bees lived 

 J. 5 days, on ari avei'age, vvifli a miriiinutn of 0.7 and a maximum of 

 2.7. Three samples of the dead bees yielded on analysis an average 



