Apiaky Experiments. 9 



greater when the comb is more than an inch thick), then the thick- 

 ening ot the cell wall by .01 of a millimeter increases the weight of 

 comb one inch thick as much as thickening the midrib .10 of a 

 millimeter. 



The thickness of the cell walls is much less than that of the 

 midrib. In natural worker comb I have found it varying between 

 .045 and .07 of a millimeter, with an average of not more than .06 

 of a millimeter (.0024 of an inch). It has been thought by some 

 that, though the bees may leave a heavy midrib in comb built on 

 foundation, they will thin the cell walls down to the thickness in 

 natural comb. 



Although the cell walls of a large number of sections of comb 

 have been measured under the camera of a compound microscope, 

 it is difficult to give these in tabulated form, as there is so much 

 irregularity in thickness. The heaviest part, except the extreme 

 outer end, is close to the base of the cell, and the thinnest is beyond 

 the middle of its length. Where comb on heavy foundations was 

 studied, the bases of the cells were found to have distinctly 

 thickened walls for some distance out, and this thickening was often 

 quite irregular, as may be seen at o in Figures g, h, and i of Plate 2, 

 and Figure b of Plate 4. 



None of the foundations used in the experiment gave as deli- 

 cately thin cell walls as are found in natural worker comb, except 

 the thin and extra thin super foundations and, possibly, the rather 

 shallow deep-cell foundation put out in 1899, which was placed 

 upon the market by the A. I. Root Co., and which is being sold 

 quite largely this year. I was not able in many cases to detect by 

 measurements that the cell walls on these foundations exceeded the 

 average thickness in natural comb. The difference, if any, is very 

 slight. Figure g in Plate 4 shows the thickness of the cell walls of 

 this foundation in cross section, and at b of Plate 6 is shown a sec- 

 tion of the walls parallel to the midrib and quite close to it. Figure 

 a of Plate 5 is a section of fully drawn comb on this foundation, and 

 it will be seen that the cell walls have nearly, or quite, the delicacy 

 of those in natural comb. 



The "1898" deep-cell foundation with considerably longer cell 

 walls, as shown at d of Plate 4, was not nearly so well worked ac- 

 cording to my measurements. This may be due to the fact that 

 the walls are so high that the bees cannot reach to the bottom with 

 their mandibles to take hold of them and pinch them to the natural 

 thinness. They can only, thjn the lower portion of the walls by 

 scraping them. As a rule, I have found the lower portion of the 

 cell wails of comb on this foundation as thick as those built on the 

 very heavy foundations, while in some cases they have been thinned 

 very nearly to the delicacy of the walls in natural comb. A good 

 illustration of the latter case is shown at the upper half of a of 

 Plate 4, but even this sample compared with natural worker comb 



