Active female courtship behavior and male nutritional contribution to female fecundity in Bruchidius dorsalis (Fahraeus) (Coleoptera : Bruchidae)

Mating behavior and the male's contribution to female fecundity were studie d in the bean weevil Bruchidius dorsalis (Fahraeus) (Coleoptera: Bruchidae) in comparison with two other species, Callosobruchus chinensis (which infe sts stored beans) and Kytorhinus sharpianus (which feeds on wild legumes). Only females of B. dorsalis showed multiple mating and characteristic preco pulatory behavior that appeared to solicit the male's nutritious secretion. In contrast, all females of the other two species did not copulate multipl y and did not show such precopulatory behavior. In B. dorsalis, the decreme nt of male body weight just after copulation indicated that seminal fluid w eighing as much as approximately 7% of the male's body weight was transferr ed to the female. Fecundity was more than eight times higher in females tha t had copulated ten times than in females that had copulated only once, ind icating that males paid most of the nutritional cost of egg production. The se facts suggest that the sex role is reversed in B. dorsalis.