| A Biometrical Study
of the Influence of Size of Brood Cell Upon the Size and Variability
of the Honeybee (Apis mellifera L.) by Roy A. Grout, 1931 |
| EXPERIMENTAL A. Purpose of Study The purpose of this experiment is to scientifically study the increase in size and variability of the worker bee as influenced by its rearing in brood cells constructed by worker bees on artificial foundation having an enlarged cell base. Three different cell sizes were used in this experiment. The number of cells per square decimeter were, 857, 763 and 706. The foundation having 857 cells per square decimeter is the standard commercial size manufactured in the United States while the two latter sizes approximate that having 750 cells per square decimeter which has been manufactured since 1896 by Jos. Mees Sons of Herenthals, Belgium and that having 700 cells per square decimeter which the same firm has manufactured since 1927. B. Methods and Materials. The foundation used in the experiment was furnished by Dadant and Sons, of Hamilton, Illinois. The sizes furnished were 857 cells per square decimeter (standard size manufactured in the United States), 763 cells per square decimeter and 706 cells per square decimeter. The two latter sizes were selected by Mr. H. C. Dadant and are approximately the same sizes as those being placed on the market by foundation manufacturers in Belgium and parts of France. The cutting of special dies and the manufacturing of the foundation were personally superintended by Mr. Dadant in order that the resulting cell bases should be true hexagons. The foundation received with the first shipment contained 7 vertical wires embedded in each sheet of wax. In addition to the vertical wires 4 horizontal wires were placed in the frames and embedded in each sheet of wax by hand. Some trouble was experienced with this foundation due to its warping between the embedded wires in warm weather. In the second shipment the foundation contained 10 wires embedded in the vertical position, which, when placed in a frame wired with 4 horizontal wires, did not warp and resulted in perfect combs when drawn out by the bees. Some combs were used which had been constructed from special foundation placed in certain colonies during the summer of 1929 by Dr. O. W. Park. To facilitate recognition and handling of the combs, the system used by Dr. Park in marking the frames was followed in this experiment. The frames containing the standard-size foundation, having 857 cells per square decimeter, were marked "A" and one notch was cut in the top-bar. Likewise, the frames containing the foundation having 763 cells per square decimeter were marked "B" and two notches were cut in the top-bar; while the frames containing foundation having 706 cells per square decimeter were marked "C" and three notches were cut in the top-bar. Since it is a well established fact that under normal conditions bees will extend the side walls of the cell and construct a comb containing cells of the same diameter as the imprint of the cell base on the artificial foundation, no control of size of cell other than special foundation was exercised. Frames containing all three sizes of foundation were placed in each of 23 colonies of the Iowa State College Apiary early in the summer of 1930. In general, two frames of each size were placed in each colony. Individual colony records were kept and the queens were marked by clipping the right wings of those reared in an even-numbered year and left wings of those reared in an odd-numbered year. An effort was made to collect the bees upon emergence from all three sizes of cells in a single colony at approximately the same time and under the same conditions. For this purpose a chart was made whereby the daily emergence of the bees from each size of cell was kept for all of the 23 colonies. Each frame was caged in a Root Nucleus Introducing Cage a day or two before the time of emergence and a selected area of brood was covered with an additional small screen cage insuring that the emerging bees would have no access to any nectar or honey. During the honeyflow, it was often difficult to find an area of brood that did not contain some uncapped cells of nectar and honey, and bees were not collected from such combs. Each sample collected from a brood comb contained at least 50 bees. During the summer of 1930, over 6000 bees were collected. During June of 1931, over 600 bees were collected. From these collections, approximately 3500 were selected as being most suitable for the experiment. The bees of this group were in sets of 150 bees consisting of three samples of 50 bees each taken from each of the three sizes of cells from the same colony, from the same mother and at approximately the same time. After collecting each sample, the bees were slightly anesthetized, either with ether or calcium cyanide, and then killed by dropping into boiling water. This method of killing, as shown by Alpatov (3), caused the proboscis to be fully extended. The sample was then preserved in a 70% alcohol solution for further treatment. The general plan of procedure for measuring the size of the individual bees of a sample consisted of the following treatment: (1) Determining the weight of the individual bee. (2) Dissecting the right fore wing, the third tergite, the fourth tergite and the proboscis of each individual bee. (3) Mounting these parts for measurement. (4) Measuring the parts. Experiments showed that an individual bee taken from a 70% alcohol solution, dried for a few minutes on a filter paper and placed on a chemical balance lost weight faster than it could be accurately weighed. It was thought best, therefore, to take the individual dry weight of each bee. Further experiments were run which showed that, by removing the bees from the 70% alcohol solution, drying on filter paper for several minutes to remove excess preservative and placing the sample in a De Khotinsky Constant Temperature Oven Appliance at a constant temperature of 70 degrees centigrade for 48 hours, the individual bees of the sample no longer lost any appreciable weight. The sample was then placed in a desiccator containing concentrated sulfuric acid. Further experiments showed that after 72 hours the bees had become thoroughly dried and no appreciable loss of weight occurred. The individual bees were then taken from the desiccator and weighed by means of an Eimer and Amend chemical balance accurate to 0.1 mg. A container of fresh calcium chloride was kept within the chemical balance at all times to dehydrate the contained atmosphere. It was also found that the repeated opening of the desiccator during a long serias of weighings caused the individual bees to increase in weight. This necessitated the weighing of a test sample at intervals during an extended series of weighings to determine the average gain in weight of the individual bees. All weights given in this experiments have, therefore, been corrected for this factor. |