BUEEAU OF ENTOMOLOGY. 235 



value greatly, and recommendations have accordingly been made to 

 all the manufacturers to build their hives with insulated bottoms in 

 the future. The results of these comparative tests have not been 

 published, but will be included with other data in a general publica- 

 tion on the results of experiments in outside wintering. In connec- 

 tion with the testing of these hives, various insulating materials were 

 tested, and it was found that the choice of an insulating material is 

 of minor importance, since the materials commonly used — shavings, 

 sawdust, leaves, and chaff — do not differ greatly in insulating value. 



During the year sufficient progress was made in the work on out- 

 side wintering to justify the issuing of a farmers' bulletin (No. 695), 

 giving general directions for wintering in this way. In this bulletin 

 the danger to the colony of excessive heat production is pointed out 

 for the first time, and special emphasis is laid on the necessity of pro- 

 tection from wind. 



Beekeepers have repeatedly claimed that excessive insulation is even 

 more detrimental in winter than insufficient insulation, because of 

 the failure of the colony to warm up on bright days. To test this 

 theory, a colony was packed in the fall of 1915 with 16 inches of saw- 

 dust on all sides, top and bottom. Temperature records were made 

 at frequent intervals every day throughout the winter and spring. 

 The colony remained in excellent condition in every respect through- 

 out the winter, being little affected by high winds, and after brood 

 rearing began it built up with great rapidity. Then, to continue ob- 

 servations on the effect of insulation on the building up of the colony, 

 the packing was allowed to remain all summer. Except for the im- 

 possibility of manipulating the colony, it remained in excellent con- 

 dition. It seems clear, therefore, that beekeepers need not fear any 

 detrimental results from abundant insulation at any season of the 

 year. 



The work of the last four winters has been chiefly on responses to 

 changes in environmental conditions, as shown by the temperature 

 reactions of the colony. To determine the reactions in actual heat 

 production, a preliminary experiment with a colony of bees in a 

 respiration calorimeter was carried out in the fall of 1915, in cooper- 

 ation with the Office of Home Economics, States Relations Service. 

 Observations were made on the oxygen consumed, the carbon dioxid 

 produced, and the heat generated. Because of the excessive size of 

 the respiration calorimeter used, it was impossible to get results of 

 the desired accuracy as to the amount of heat generated, but valuable 

 results were obtained in the other phases of the investigation which 

 throw much light on the amount of ventilation needed in winter. It 

 is planned to continue this work during the coming autumn with a 

 specially constructed respiration calorimeter. 



During the course of the investigation of the wintering of bees 

 about half a million temperature records have been made, together 

 with records of meteorological conditions. These have been charted 

 as rapidly as possible, but it was not practicable to keep up with all 

 the charts. During the winter of 1915-16 the number of colonies 

 under observation was reduced to permit the study of the charts of 

 previous winters. This work is now practically complete, and it is 

 hoped that the results of the various experiments may be prepared 

 for publication in the near future. 



72412°— age 1916 16 



