Miyanga et al. (2006) describe four nests of Halictus senilis excavated in Kazakhstan. Two were found in an embankment of loose and powdery sand in sparsely vegetated desert, and the other two in an embankment along a dirt road in riparian forest. The authors provide illustrations of the nest site and diagrams of the nests. Cells were concentrated along the main burrow (as opposed to being spaced evenly), and radiated out in all directions (as opposed to being along one side). The cells were attached directly to the burrow rather than connected by lateral burrows. A blind burrow extended below the areas with the cells. The burrows were ~20 cm deep. Two nests contained many cells (15 and 16), while the other two contained only one and two cells. The authors discuss the nest architecture in the context of the bees’ social behavior. Although only one female was found in each nest, the close spacing of immature offspring in the two bigger nests suggests that two females may be laying eggs. Previous authors proposed that H. senilis may have delayed eusociality, in which a nest is initiated by one female in one season, and then her daughters overwinters with her so that in the second season, the original female is a queen and the daughters are workers. In this scenario, the two large nests may represent eusocial colonies, and the smaller nests first-season colonies.
