The Race for Females: The Mating System of the Red Mason Bee, Osmia rufa (L.) (Hymenoptera: Megachilidae)

The ecology of a species strongly influences the strategies with which males and females maximize their lifetime reproductive success. When males and females do not invest equally in offspring, the sex with the higher parental investment becomes a rare resource for the other. The spatial and temporal distribution of the limiting sex forms the basis of the mating system. In nest-constructing Aculeata such as the red mason bee, Osmia rufa, females perform intensive brood care, whereas males do not invest in their offspring but instead compete for access to mates. Receptive females of this species are widely distributed and do not assemble at certain places. Therefore, territorial behavior is not an advantageous mating tactic for males, which instead search for females within individual home ranges usually centered around food plants. The unmarked or defended home ranges of different males may completely overlap. Competitive searching leads to a random distribution of matings among males that is largely independent of body size. The mating system of O. rufa can be described as scramble competition polygyny.