80 



MASS. EXPERIMENT STATION BULLETIN 234 



The daily mortality, the mean hourly temperature during the part of the 

 day bees were active, the weather conditions and the activity of the bees 

 during the experiment were as follows: 



April 



30 

 May 

 1 

 2 

 3 

 4 

 5 



No. 

 Dead 

 Bees 



16 

 20 

 109 

 110 

 127 

 94 

 tif) 



4« 

 1U7 

 115 



118 

 156 

 94 

 81 

 129 

 129 



186 



177 



Mean 

 Hourly 

 Temp. 

 " Fahr. 



42° 



50° 

 52° 

 57° 

 61° 

 58° 

 54" 

 54° 



51° 

 55° 

 63° 

 60° 

 60° 

 65° 

 67° 

 56° 

 65° 

 70° 



61° 



64° 



71° 

 70° 



Weather and Activity of Bees 



Cloudy (rain) ; little artivity 



Cloudy; little activity 



Clear; active 



Clear; active 



Cloudy; fairly active 



Cloudy, inactive 



Cloudy (little clear) ; inactive 



Cloudy; almost no bees active 



Cloudy; almost no bees active 



Cloudy; almost no bees active 



Clear; bees fairly active 



Cloudy, rain all day; no bees active 



Clear; bees active 



Clear; bees active 



Clear; bees active 



Cloudy, rain; very little activity 



Cloudy; very little activity 



Clear, later cloudy; very little 



activity 

 Clear, cool wind ; some bees out 



and active 

 Clear, cool v/ind; few bees out 



and active 

 Clear; bees fairly active 

 Clear; bees fairly active 



Remarks 



Blossoms opening 

 Combined spray 



Bloom at height 

 Combined spray 



Blossom petals dropping 



Bloom about all gone 



.Apple blossoms introduced 

 Lead arsenate alone 

 Fresh blossoms introduced 



Bloom about all gone 



Considerable unevenness was noted in the opening of blossoms, so that 

 throughout the experiment there were always many blossoms not covered 

 by the spray. 



Before the sprays were applied, bees worked the blossoms freely. They 

 were very strongly repelled by the spray, however, particularly before it 

 had dried. Several hours after the trees were sprayed, a few bees were 

 observed to be visiting tiie trees. 



Unfavorable weather conditions during the period of the experiment 

 allowed but brief and infrequent activity of the bees, so that only slight 

 correlation was shown between the time of spraying and the mortality of 

 the bees (Fig. 1). The only mortality which could be given any signifi- 

 cance followed the application of lead arsenate alone. Even then, the 

 number of bees killed was comparatively small. 



The following season ' (1926) the experiment was repeated. A normal 

 ten-frame colony was introduced into the tent on May 3. The bees were 

 allowed several days in which to become accustomed to their surroundings 

 before the daily record of mortality was made. This was possible because 

 of the fact that the colony was introduced a number of days before the 

 blossom buds began to open. 



Weather conditions were on the whole more favorable for bee activity 

 than was the case in 1925. In both seasons, however, there was consider- 

 able unevenness in the opening of bloom, which furnished a continuous 

 supply of newly-opened blossoms, so that after each spray bees had fresh 

 unsprayed bloom available. 



At the close of the blooming period of the peach, apple bloom was plenti- 

 ful. The experiment was extended to cover a good part of the period of 

 apple bloom, which allowed two extra applications of spray. The supply 



