## 4 Discussion
The lack of significant differences in the sum of the widths of the third and fourth tergites in spring and the decline in the sum of the tergites in summer could be indicated by the higher density of cells in the area of the comb, which ensures better temperature conditions for rearing a bigger amount of brood in the same area of the comb in smComb compared to STComb. The present study, likewise the experiments conducted by [PERSON] and [PERSON] [11] as well as [PERSON] and [PERSON] [14] and our previous findings [15], indicated the relatively constant body size of workers and a lesser effect of the width of comb cells than was previously assumed. However, the results are not in agreement with findings reported by [PERSON] [6,7], who observed an increase in the worker body size corresponding to changes in the width of the rearing cells. The small-cell combs provided comparable rearing conditions to the standard-cell combs; however, the colony kept on the small-cell combs ensured worse conditions for the brood reared in the standard-cell combs. Bees reared in the STComb + smColony variant exhibited a lower value of the head width, head height, thorax width, and fore wing width and length than those reared in the STComb + STColony combination. In turn, they did not differ in the sum of the widths of the third and fourth tergites, i.e., one of the measures of the worker's body size proposed by [PERSON] [6,7]. The values of most morphometric parameters of the STComb + smColony workers were lower than those in the smComb + smColony and STComb + STColony groups. This indicates that the width of the comb cells does not determine the size of the worker's body. Other elements of rearing are regarded as equally important, e.g., the quality of feeding larvae, which was confirmed by [PERSON] et al. [8]. [PERSON] et al. [22] reported that workers reared in standard-cell combs feed larvae more abundantly than workers reared in small-cell combs. We find it particularly advantageous to place small-cell combs in a colony maintained on standard-cell combs. In our other studies, it resulted in a significantly higher value of the functional traits of such colonies compared to colonies kept only on combs of one type, with only small- or only standard-cells [23]. We assume that such a combination may modify the division of labor in the worker caste ([PERSON], [15,24]. The absence of significant differences in the values of traits most often used in the identification of worker subspecies, i.e., the proboscis length, cubital index, and the sum of the widths of the third and fourth tergites, between the assessed worker groups (smComb + smColony, STComb + smColony, and STComb + STColony) indicates the low dependence of these parameters on changes in rearing conditions. This confirms the high suitability of these parameters for the identification of honeybee subspecies. The results of the morphometric measurements of the F1 generation of Buckfast worker bees analyzed in the present study indicate that they represent large-body size bees. In the STComb + STColony variant, the values of the most frequently assessed morphometric parameters, e.g., the proboscis length (6.71 mm) or the length and width of the fore wing (9.56 mm and 3.22 mm, respectively) were within the upper limits of the range for honeybees. In turn, the sum of the widths of the third and fourth tergites (4.84 mm) exceeded the range for honeybees (value range: proboscis length 5.02-7.26 mm, fore wing length 7.46-9.75 mm, fore wing width 2.64-3.31 mm, sum of the widths of the third and fourth tergites 3.63-4.76 mm) [6]. Such high values may be associated with the fact that we assessed F1-generation workers derived from naturally mated queens, which may have caused heterosis. In a study of the morphometric traits of pure Buckfast bees, [PERSON] and [PERSON] [25] reported slightly lower values of the sum of the widths of the third and fourth tergites (4.79 mm) and proboscis length (6.36 mm).