Sex Ratio of Small Hive Beetles: The Role of Pupation and Adult Longevity

Abstract

The sex ratio of sexually reproducing animal species tends to be 1:1, which is known as Fisher’s principle. However, differential mortality and intraspecific competition during pupation can result in a biased adult sex ratio in insects. The female-biased sex ratio of small hive beetles (SHBs) is known from both laboratory and field studies, but the underlying reasons are not well understood. Here, we used laboratory mass and individual pupation to test if differential mortality between sexes and/or intraspecific interactions can explain this sex ratio. The data show a significant female-biased adult sex ratio in both mass and individual rearing, even when assuming that all dead individuals were males. Our results therefore suggest that neither differential mortality during pupation nor intraspecific interactions are likely to explain the female-biased sex ratio of freshly emerged adult SHBs. We regard it as more likely that either competition during the larval feeding stage or genetic mechanisms are involved. In addition, we compared our data with previously published data on the sex ratio of both freshly emerged and field-collected SHBs to investigate possible gender differences in adult longevity. The data show a significantly greater female bias in the sex ratio upon emergence, compared to field-collected SHBs, suggesting that adult females have a shorter longevity.

Ubiquitous but Ignored? A Case of Water Beetle in Southeastern Europe

“…Substrate type also proved to be an important factor in determining differences between male and female abundances in the Spring of the Bijela rijeka River (CRO) (p = 0.001, p ≤ 0.001) and upper reach of the Bijela rijeka River (p = 0.001, p ≤ 0.001), as shown in Figure 8. Elliot [86], in his study of four elmid species, found that the sex ratio was 1:1 according to Fisher's principle [91,92], a result that was also found for E. bosnica in the Spring of the Bistrica River. In the other springs and habitats studied, however, the ratio was in favor of males, especially in the winter months; this could be explained by the emergence of females in summer [88,89].…”

“…Substrate type also proved to be an important factor in determining differences between male and female abundances in the Spring of the Bijela rijeka River (CRO) (p = 0.001, p ≤ 0.001) and upper reach of the Bijela rijeka River (p = 0.001, p ≤ 0.001), as shown in Figure 8. Elliot [86], in his study of four elmid species, found that the sex ratio was 1:1 according to Fisher's principle [91,92], a result that was also found Although the sex ratio is known as one of the key parameters for knowing the biology of any species, there are few data in the literature on Elmidae [86,[88][89][90]. Sex ratios of E. bosnica in four studied karst springs differed at spatial and temporal scales (Table 3).…”

Does space matter? Estimation and evaluation of required space for commercial mass culture of grasshoppers (Acridoidea: Orthoptera)

“…We did this on purpose, even though there were ways to determine the BMIs for each sex and link them to mortality. Since the sex ratio of an individual tends to be fairly equal according to Fisher’s principle [ 61 ], we assumed that when farmers culture grasshoppers on a large scale, both males and females would be present in roughly equal ratios in the rearing cabinets [ 62 ]. In contrast, by displaying BMI data separately for males and females and linking them with mortality, it would encounter difficulties in associating space with BMI for a species, as the dual BMI (male and female independently) does not accurately reflect reality in culture cabinets since both sexes present there in almost equal force simultaneously.…”

Cuticular Hydrocarbon Profile of Parasitic Beetles, Aethina tumida (Coleoptera: Nitidulidae)

“…In brief, freshly hatched SHB larvae were fed by providing them with a honey bee worker brood frame until they had reached the post-feeding wandering stage and then transferred into a 473 mL glass jar filled with suitable autoclaved soil for pupation. Pupation containers were kept at 25 • C, 80% RH, 24 h dark until adult emergence [46]. Upon emergence, adult SHBs [N = 10] were kept in incubators with sugar water [45] for seven days and then freeze killed for further chemical analysis.…”