| Influence
of Size of Brood Cell Upon the Size of the Worker Bee* By Roy A. Grout,** Illinois |
| The late Monsieur Ursmar Baudoux
of Belgium was the first to conceive of the use of an artificial foundation having an enlarged cell base to increase the size of the emerging bee. In the year 1893 he was amazed on discovering bees from an old skep which were very much smaller than normal. He then conceived the idea of raising bees in larger cells. He accomplished this by means of stretching regular foundation to the size he desired and had by 1896 sufficiently proved his point in Belgium that a manufacturing company began to place upon the market artificial bee comb foundation having enlarged cell bases. It was Baudoux's belief that the nurse bees following a natural instinct filled the bottom of the enlarged cell more copiously with larval food, and that this caused an increase in the size of the worker bees He also intimated that the larger bee would generate more body heat which would result in a greater quantity of brood. By means of stretching foundation, he experimented with various sizes of foundation having 750 cells to the square decimeter, 740, 730, 710, 700 and even 675 cells per square decimeter. (This is in contrast to the U. S. standard size which is 857 cells per square decimeter.) By means of an ingenious glossometer of his own make, he determined the tongue reach of his colonies and by means of an equally ingenious thoraxometer of his own make, the diameter of the thorax. He found that with an increase of 50 cells per square decimeter in the size of the foundation, there was a corresponding decrease of one half millimeter in the tongue reach. His thoraxometer gave thorax diameters of 3.7 mm., 3.9 mm., 4.1 mm. and 4.3 mm. for worker bees reared in brood cells built from foundation having respectively 850, 800, 750, and 700 cells per square decimeter. He arrived at the conclusion that artificial foundation having 700 cells per square decimeter gave a bee which was superior in all its measurements to those reared in combs constructed from the smaller sizes of artificial foundation. Independent of the work done by Baudoux, a Frenchman by name of Pincot arrived at the idea from a slightly different angle. Pincot noticing the difference in size of worker bees from a swarm placed on foundtion and the worker bees of the parent stock reared in natural combs, came to the conclusion that this was due to the fact that the natural brood cells were larger than those drawn from the foundation and actual measurements confirmed his theory. He then started experimenting with foundation having 736 cells per square decimeter and reports that during a two year period thirty colonies using this size of foundation gathered approximately one - third more honey than did thirty colonies on normal foundation. Unfortunately, in 1910 his apiaries were destroyed by a flood and Pincot was forced to abandon his experiments. While the experiments of these two cannot be considered of a very scientific nature, each claimed larger bees resulting in a greater yield of honey. Their activities, particularly those of Baudoux, were convincing to the extent that a firm in Belgium has offered enlarged cell foundation for sale since 1896. Other manufacturers have followed in this course. France was next and more recently Italy and England have manufacturing concerns offering for sale enlarged cell foundation and claiming better results through its use. Consequently, interest in this country has been focused upon this matter. A Russian worker by name of Lovchinovskaya reporting on experiments started in 1925 using enlarged cell foundation showed that bees reared from enlarged cells weighed more, had a greater load capacity and that from the results of one season produced more honey. During the period 1930 to 1932, the first scientific study was made to determine the effect of rearing in enlarged brood cells upon various parts of the worker bee. These experiments were carried on at Iowa State College under the direction of Dr. 0. W. Park. Three different sizes of foundation were used having respectively 857, 763 and 706 cells per square decimeter. The foundation having 857 cells per square decimeter is the commercial size manufactured in the United States. The foundation having 763 cells per square decimeter closely approximates that having 750 cells per square decimeter which has been manufactured since 1896, by Jos. Mees Sons of Herenthals, Belgium, and the latter size closely approximates that having 700 cells per square decimeter which the same firm has manufactured since 1927. Care was taken to eliminate all warp and sag in the finished comb and no control of size of brood cell other than size of foundation was used. To facilitate recognition and handling of the combs, and for convenience in presenting date, the frames containing the standard size foundation, that having 857 cells per square decimeter, Were marked "A" and the cell size was referred to as size of cell "A". Similarly, frames containing foundation having 763 cells per square decimeter were marked "B" and the cell size was referred to as size of cell "B". Likewise, the frames containing foundation having 706 cells per square decimeter were marked "C", and the size of cell was referred to as size of cell "C". In general, two frames of each size of foundation were placed in the same colony. Individual colony records were kept and the queens were marked by clipping the right wing of those reared in an even numbered year and the left wing when reared in an odd numbered year. It is of interest to mention that difficulties were experienced in getting the queens to oviposit worker eggs in the enlarged cells when all three sizes were placed in the same hive at the same time. This was particularly true in case of size of cell "C". While the worker bees apparently recognized no difference in accepting the three sizes of cells, the queen bees showed a preference for the smaller cells for ovipositing. This result was confirmed by similar experiments carried out by Lovchinovskaya. 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. To determine the date of emergence, a chart was used whereby the daily emergence of bees from twenty-three colonies was recorded. Prior to emergence, each frame was caged in a Root introducing cage and a selected area of brood containing no nectar or honey was caged with an additional screen cage. Each sample of bees contained at least fifty specimens. Following the method outlined by Alpatov of Russia the bees were slightly anaesthetized and then killed by dropping into boiling water. They were then preserved in a 70 percent alcohol solution to await further treatment. The measurements taken on each individual bee were dry weight. length of right fore wing, width of right fore wing, the sum of the widths of the third and fourth tergites and the length of proboscis. In Plate 1 are shown the measurements taken on the right fore wing, the third tergite and the fourth tergite. (In explanation the two latter parts are the two largest plates on the top of the abdomen.) Plate 2 shows the measurements taken on the tongue or proboscis. In the series of graphs which are illustrated, each character, namely, dry weight, length of proboscis, length of right fore wing, width of right fore wing, left fore wing and the sum of the widths of the third and fourth tergites is plotted for each size of cell. In all cases there is a distinct trend towards a larger character of the worker bee as the size of the brood cell increases. In table 1 are given the averages of the five measurements for the bees from each size of cell and the percent increase of these measurements. It is of interest to note that the length of proboscis increased 2.07 percent as the size of foundation was increased from 857 cells per square decimeter to 706 cells per square decimeter. We, therefore, find that the size of the brood cell is definitely a factor in determining the size of the adult worker bee. It is also apparent that larger bees are obtained through the use of artificial bee comb foundation having enlarged cell bases. It is reasonable to state when we compare a 2.07 per cent increase in the length of the tongue, that size of brood cell alone is not sufficient to produce a much larger bee. It is much more reasonable to state that selection and breeding of bees plus the application of such factors as size of brood cell should accomplish marked results in producing larger bees. From the results we have obtained we cannot agree with Baudoux either in the results he obtained or the consistency of his results. While he records increases of 11.9 per cent to 25 per cent in length of proboscis as the size of the brood cell increases from 850 cells per square decimeter to 700 cells per square decimeter we are only able to find an increase of 2.07 per cent as a maximum. However, we believe that our results compare favorably with results obtained by Michailov of Russia who, on measuring the tongues of worker bees reared in worker cells as compared with those of worker bees reared in drone cells, found an increase of 4.82 per cent. While this is a greater increase than ours, it must be considered that the size of cell was increased slightly more than twice as much as in this experiment which in all probability would account for the difference. Our results also compare favorably with those obtained by the same worker on worker bees reared in new combs as compared with worker bees reared in old combs. Here Michailov records an increase of 1.05 per cent in the length of the tongue. Since we have made the statement that size of brood cell alone is not sufficient to produce a much larger worker bee, we must consider the fact that the crucial test for the commercial use of enlarged foundation is greater honey production. While this experiment should be a strong indication toward that end, the exact relation of this increase in the size of adult worker bees to a greater yield of honey has yet to be proved. During the past four years, we have been conducting an experiment in a commercial yard with from fifteen to twenty colonies containing brood combs constructed from each size of foundation, making an apiary of sixty colonies maximum. To date we have not been able to find any significant increase in the honey production due to the use of enlarged cell foundation. This experiment is still being continued in a location more favorable for honeyflows and we expect to have some definite results in the near future. *Rewritten from Journal Paper of the Iowa Agricultural Experiment Station. Ames. Iowa. Project No. 129. **Formerly. Research Assistant in Apiculture, Iowa Agricuitural Experiment Station, Ames, Iowa. |