First Steps into Eusociality: The Sweat Bee Dialictus lineatulus

Abstract

The primitively eusocial halictid bee Dialictus lineatulus has two generations per year in New York. Spring nests are initiated by one to six female bees; in multifoundress nests all bees are potentially reproductive but the largest individual doesn't forage. Summer nests contain an average of seven female bees which occur in reproductive castes, with workers almost the same size as queens. Some summer nests briefly form eusocial colonies where the foundress queen lives with her worker daughters. Foundress bees soon die in the summer, and most nests are then semisocial and contain only summer generation bees. The replacement queens are the dominant and older sisters of the workers. I hypothesize that reproductive castes first evolved in such sister associations due to environmental factors that prohibit subordinate bees from leaving and successfully starting their own nests.