Transvestism Hypothesis: a Cross-Sex Source of Morphological Variation for the Evolution of Parasitism Among Sweat Bees (Hymenoptera: Halictidae)?

Brood parasitism has evolved repeatedly in insects, and is especially diverse within bees. Little attention has been given to the evolution of structural modiÞcations associated with parasitism, in contrast to behavior. Female parasitic bees tend to converge on a suite of characters, some of which may involve loss of characters associated with pollen-collecting or nest-making, whereas others may represent new characters used in a parasitic lifestyle. Certain external traits of female parasites resemble those of males, and this study compares the phenetic similarity of males and females of a social parasite, Paralictus asteris Mitchell, and its host, Lasioglossum (Dialictus) imitatum (Smith). Results are consistent with the hypothesis that some structural traits associated with parasitism may be derived from the expression of male-like traits in females.