| 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 C. Presentation of Data. 1. The size of the worker bee as influenced by size of brood cell. A study of the three sizes of cells used in this experiment and their relation to each other reveal the following data. To facilitate an understanding of this and following data the size of the cell contained in a comb having 857 cells per square decimeter will be designated as size of cell "A"; the size of cell contained in a comb having 763 cells per square decimeter will be designated as size of cell "B"; in a similar manner the size of cell contained in a comb having 706 cells per square decimeter will be designated as size of cell "C". Between the sizes of cells "A" and "B" there is a reduction of 94 cells per square decimeter and between the "B" and "C" sizes there is a reduction of 57 cells per square decimeter, making a total reduction of 151 cells per square decimeter between the "A" and the "C" size. It was also thought advisable to investigate the increase of linear measurement of the cell and it was found that there was an increase of 5.98% in the diameter of the cells between the "A" and the "B" size, an increase of 3.96% between the "B" and the "C" sizes and an increase of 10.18% between the "A" and the "C" sizes of cells. From the bees collected during the summer of 1930, data are presented in this thesis on the bees from three colonies. A sample containing at least fifty bees was collected from colony 25 from an "A" comb on August 21, 1930. One week later, on the 28th of August, two samples of bees were collected from a "B" and a "C" comb, respectively. The bees from colony 21 were collected within a period of two days, two samples being collected from an "A" and a "B" comb, respectively, on August 18, 1930, and a third sample from a "C" comb on August 20, 1930. The bees from colony 18 were collected over an extended period of time. One sample was taken from an "A" comb on August 30, 1930, another from a "C" comb on September 7, and the third from a "B" comb on September 23. The individual hive records of these three colonies show that the bees from each colony were the progeny of the same mothers. From the samples of bees collected from colony 25, complete data were obtained on 44 bees of the sample from the "A" comb, 47 bees from the sample from the "B" comb and 45 bees from the sample from the "C" comb. Similarly, data are presented on 40 bees from the "A" comb from colony 21, 43 bees from the "B" comb and 45 bees from the "C" comb. In the case of colony 18, complete data were obtained on 41 bees from the "A" comb, 48 bees from the "B" comb and 50 bees from the "C" comb. The influence of the increase in the size of the brood cells upon the size of various measurements taken on the parts of the individual worker bees of colony 25 is shown in Table 1. The measurements presented for comparison, given in column 1, are dry weight, length of right fore wing, width of right fore wing, sum of the widths of the third and the fourth tergites, length of proboscis, length of mentum, length of glossa and the sum of the lengths of the mentum and the glossa. In the second, fourth and sixth columns are given the arithmetic mean of each measurement and the standard deviation of the mean on the groups of bees from each of the three sizes of cells. In the third column are given the differences between the arithmetic means of the bees from size of cell "A" and the bees from size of cell "B" and the standard deviation of the mean difference. The differences between the means of the bees from size of cell "B" and the bees from size of cell "C" are presented with their standard deviations in column 5. Similarly, the differences between the means of bees from size of cell "A" and size of cell "C" are presented with their standard deviations in the seventh column. The values of the mean differences that are statistically significant are starred. The test for significance was accomplished by dividing the mean difference by its standard deviation and comparing the resulting values with the corresponding "t" values given in Table 16 by Wallace and Snedecor (69). All values of the mean differences between the 8 characters of bees from size of cell "A" and bees from size of cell "B" are statistically significant and are therefore greater than would be the case if the bees were selected at random from the same population. In a comparison of the values of the bees from size of cell "B" and size of cell "C" it is shown that, with the exception of length of mentum, all means of the bees from size of cell "A" and size of cell "C" differ significantly in all eight cases. In Graph 2 is presented a frequency diagram of the character dry weight for each of the three samples of colony 25. An examination of the three curves, each representing the frequency distribution of the bees from one size of cell, shows that not only do the arithmetic means and peaks of the curves differ widely but also the distributions, since the curves scarcely overlap. There is also a difference in the types of the curves. While the curves representing the frequency distribution of the dry weight of bees from size of cell "A" and size of cell "B" are quite similar, the curve representing the dry weight of the bees from size of cell "C" shows a much more extensive distribution. The frequency distribution of the character length of right fore wing is presented graphically in Graph 3. It is of interest to note that there is a trend in the peaks of the curves and the frequency distributions showing that not only do the means of the groups differ significantly but that the group as a whole tends to increase in size as the size of the cell, with which it is associated, increases. The frequency distributions of the characters, width of right fore wing, sum of the widths of the third and the fourth tergites and the length of proboscis are presented graphically in Graphs 4, 5 and 6, respectively. The curves of Graphs 4 and 5 show that there is a trend both in the peaks of the curves and in the curves themselves toward a larger value of the measurement of the character with an increase in the size of the cell from which the sample is taken. The curves represented in Graph 6 do not show the familiar trend between the peaks of the two curves representing the length of proboscis of bees from size of cell "A" and size of cell "B". There is, however, a distinct difference between the peaks of the curves representing this character for bees from size of cell "B" and size of cell "C". The trend of the distribution curves in all three cases is from a smaller to a larger length of proboscis as the size of cell is increased. It is also of interest to investigate the percent increase of the arithmetic means of the various measurements of the bees as the size of the cell is increased. Dry weight, which is a measurement of mass and consequently volume, increases markedly from 15.50% to 51.28%, as the size of cell increases. The linear measurements show an average increase of 1.37% as the area of the cell base is increased 12.32%, an average increase of 1.00% as the area of the cell base is increased 8.07% and an average increase of 2.38% as the area of the cell is increased 21.39%. By comparing the average percent increase of the linear measurements to the increase of the diameter of the cell it is discovered that as the diameter of the cell is increased 5.98% there is an increase of 1.37% in the average linear measurement, that, with an increase of 3.96% in the diameter of the cell there is an average increase of 1.00% in the linear measurements and that an increase of 10.18% in the diameter of the cell is accompanied by a corresponding increase of 2.38% in the average measurements of the worker bees. It is of interest to note here that the ratios of the percent increases of the diameters of the cells are approximately the same as the ratios of the percent increases of the average dimensions of the worker bees. The percent increase of the linear measurements on the various parts of the bees are shown diagrammatically in Graph 1 and the percent increase of all measurements is given below in tabular form.
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