20 March 2021
A species of sweat bee found throughout the Northern Hemisphere. H. rubicundus was introduced into North America from the Old World during one of two main invasions of Halictus subgenera. These invasions likely occurred via the Bering land bridge at times of low sea level during the Pleistocene epoch.
The species exhibits different social behaviors depending on climate: it is a solitary species in high elevations or latitudes where the season is short, but eusocial in other areas. Often, solitary and eusocial colonies appear simultaneously in the same population. These sweat bees are extensively studied for their variability in social behavior, which has become a model for social plasticity. This variability has contributed to an understanding of evolution of social behavior.