April, '22] WILSON: CLIMATE AND BEE MANIPULATION 145 



keepers plan to remove the bees between April 1 and April 15. A few 

 beekeepers remove the bees as soon as the snow disappears. 



Here again the weather records of the past ten years give us an indica- 

 tion of how early the bees may be removed to advantage. 



Bees should not be taken out while the ground is covered with snow. 

 During the eight of the last ten years the temperature was high enough 

 at Madison so that the bees could have had a cleansing flight between 

 the 10th and 15th of March if the snow was melted away. However, 

 the snow does not usually disappear before the fifteenth of March and 

 after that time a suitable day for a flight is not likely to occur before the 

 twenty -third. Practically every year a warm spell occurs between the 

 twenty-second and the twenty-sixth of March so that if the bees need 

 a flight they may be set out on the twentieth or sooner, with the assur- 

 ance that they will be able to fly within a few days. In one year out of 

 ten they may be able to fly before March 10. During the same period 

 there was one year when a flight was not possible until March 26. 



If bees are known to be short of stores they should be set out during 

 the warm spell in March and given an abundance of sugar syrup to carry 

 then over until the time when they can gather nectar in the field. 



During the winter the temperature surrounding the cluster will be 

 held at 57° F. as long as the bees have stores and energy to live, re- 

 gardless of the cold outside. During that time the temperature may go 

 below the zero point for a short period at a time, but it will range mostly 

 from 20° F. or higher. The bees are then only required to develop 

 an approximate average of thirty-seven heat units. In addition, they 

 are not at that time required to use energy in the production of wax 

 and food for the young. 



As soon as brood rearing starts in the spring the temperature inside 

 the cluster and around the young brood is increased to 90 to 95° F. 

 At the same time the temperature will in the northern states run about 

 40° F., with fluctuations during March and April up to 65° F. Under 

 those conditions the bees are forced to produce energy which will keep 

 the temperature up to that of brood rearing, a difference of thirty 

 to fifty heat units. During that time an excess of energy is also being 

 used in producing larval food and possibly other products. 



A practical illustration of how temperature influences the development 

 of brood in the spring may be demonstrated by watching three colonies 

 of minimum, medium, and maximum strength. By May the weak 

 colony will have only a small circle of brood indicating the inside space 

 covered by the cluster. This will also be more or less true of the medium 

 colony, but the area of the brood nest will extend beyond the ordinary 



