Alternative Reproductive Strategies of a Gregarious Ground-Nesting Bee, Dieunomia triangulifera (Hymenoptera: Halictidae)

I studied reproductive behavior of females of the gregarious ground-nesting bee Dieunomia triangulifera (Halictidae). During peak bloom of the host plant, Helianthus annuus, some females consistently brought pollen to one nest (provisioning bees), whereas others visited many nests without taking pollen to any (searching bees). Searching bees were more likely to have two or more developed oocytes and crops full of pollen. The ingested pollen probably provided protein for egg production. The differing behavior of provisioning and searching bees combined with contrasting internal morphology, indicated that these two sets of behaviors were alternative reproductive strategies. Three possible explanations for the searching bees' behavior included: usurpation, floating, or intraspecific cleptoparasitism. Each of these is evaluated as a possible function of searching behavior. Given the evidence I conclude that intraspecific cleptoparasitism is the most likely explanation.