ABSTRACT

I propose two hypotheses regarding the relationships between halictine bee demography and social behavior and the environment: the ‘Mating Limitation Hypothesis’ (MLH), that a female's social role (‘caste’) is dependent on whether she mates while young (and thus dependent on male demography); and the ‘Environmental Control Hypothesis’ (ECH), that the decision to lay eggs of one sex or another (thus defining male demography) is dependent upon the temperature and/or photoperiodic conditions experienced at the time the egg is laid, in temperate species. Published demographic and behavioral data typically lack the precision needed for truly conclusive analysis and review, and there are some important recently discovered phenomena that were historically overlooked, and extremely difficult to document. Nonetheless, a review of the available data reveals many notable features that can help evaluate the proposed hypotheses, and offers some guidance for future research. An older hypothesis that is also addressed here is that sexual selection is expected to promote protandry, for many reasons, yet the data on halictine bees suggests that protandry is absent in social populations, although it is characteristic of solitary populations.

Geographic variation in demography and behavior is common, and this variation appears to correlate with the seasonality of the habitat, in a manner consistent with the predictions of the two proposed hypotheses.