Degree-day accumulation controlling allopatric and sympatric variations in the sociality of sweat bees, Lasioglossum (Evylaeus) baleicum (Hymenoptera: Halictidae)

A halictid bee with sympatric solitary and eusocial nests offers evidence for Hamilton's rule

“…Morphological difference between the queens and workers is small or absent 13 . Importantly, recent investigations have revealed that solitary-and multiplefemale nests occur in a single population of a halictid bee, Lasioglossum baleicum 14,15 . L. baleicum is a bivoltine bee that produces two broods per year, and multiple-female nests are found only during the second reproductive period 16 .…”

“…L. baleicum is a bivoltine bee that produces two broods per year, and multiple-female nests are found only during the second reproductive period 16 . Many colonies are constructed within a small area, producing nest aggregations [14][15][16] . Within each shallow nest ( < 10 cm below ground), a nest gallery containing several larval cells are constructed; each cell is provided with a pollen ball for rearing the larva 16 .…”

“…After a short inactive period, a second brood is reared (F2) during mid-July to mid-August. No third reproduction has been observed most likely because the season is never long enough to complete a third reproduction 14,17 . The F2 females hibernate after mating and become new F0 foundresses in the following spring.…”

“…For example, L. baleicum populations inhabiting cold areas rear only a single brood 14,17 , suggesting that early diapause is an optional strategy for F1 females. In addition, adult females occasionally intrude into an unrelated nest 14,15,19 . In a previous study, bees nesting in a shady area did not produce a second brood 14 , which indicated that a F1 female can choose early diapause or intruding.…”

“…In addition, adult females occasionally intrude into an unrelated nest 14,15,19 . In a previous study, bees nesting in a shady area did not produce a second brood 14 , which indicated that a F1 female can choose early diapause or intruding. Thus, at the start of the second reproductive period, F1 females can engage in the solitary nesting, eusocial nesting with the mother, intruding into another nest, or early diapause.…”