ABSTRACT

An overview of variability in social behavior of sweat bees shows why a consideration of environmental influences helps us understand the current distribution of halictine social behavior and how it evolved. The breadth of reaction norms for social behavior apparently varies among species, based on limited information. Conspecific attraction, mutual tolerance and group–living occur within lineages of solitary sweat bees, providing opportunities to study weakly or undifferentiated social organizations, analogous to early phases of social evolution. Perceptual capabilities to manipulate social environments are reviewed, but there is insufficient evidence to determine whether such capabilities constrain social organizations. Hypotheses relating to the importance of natural enemies for the expression of social behavior are also reviewed, but again pertinent data are scarce.

INTRODUCTION

Hamilton (1964,1972) enlarged our concept of reproductive behavior by taking into account a kinship–weighted fraction of offspring produced by collateral relatives. This gene's–eye view of reproduction clarified certain features of animal societies and their evolution, as discussed elsewhere in this volume (see also Gadagkar 1991; Mueller 1991). Similarly, we need to enlarge our concept of ‘the environment’.