A17: Plateaux-Quénu, C., L. Plateaux and L. Packer. 1989. Biological notes on Evylaeus villosulus (K.) (Hymenoptera, Halictidae), a bivoltine, largely solitary halictine bee. Insectes Sociaux. 36:245-263.
Abstract: The biology of Evylaeus villosulus was studied both in the field and in experimental rearing cages. Field caught females and their summer daughters were compared using multivariate discriminant functions analysis. The variables used were two size, two colouration and four sculpturing characteristics. All variables show significant differences between generations but the colouration and sculpturing characters did not show allometric variation within generations and may be environmentally induced. Sex ratio data are available for the summer generation for both field and laboratory reared brood. Both gave female biased sex ratios approximating 4:1. Data for the overwintering generation were obtained only from the laboratory, the sex ratio was slightly female biased - 1.2:1. Pupal weights differed significantly between generations for females but not for males. Using the appropriate values, the investment ratio is female biased in both generations; approximately 5:1 in the summer and 2:1 in the autumn. Overwintered females frequently survive long enough to forage simultaneously with their earlier emerging offspring. Cohabitation between females of the same generation occurs with low frequency but no division of labour results, rather communal colonies are formed. Similarly, when a mother and a daughter shared a nest, an eusocial colony resulted. Thus, E. villosulus would appear to be a basically solitary species despite exhibiting reduced size in the daughters of overwintered females and a female biased sex ratio, both of which are characteristics frequently associated with eusociality.