Insemination Capability of Male Pteromalus Venustus (Hymenoptera:Pteromalidae), A Gregarious Parasitoid of Megachile Rotundata(Hymenoptera: Megachilidae)

Inseminative ability in Pteromalus venusus, an arrhenotokousparasitoid presumed to have evolved under Local Mate Competition,was studied by recording the progeny production of a seriesof six virgin females presented to males at hourly intervals. Mostmales did not reach the upper limits of their inseminative abilities:Three-quarters of the males inseminated at least four females,twice the ratio of females-to-males in an average brood (2:1).There was no evidence of sperm depletion: The few uninseminatedfemales did not tend to be those presented later in the matingsequence, and a comparison of progeny production by female positionin the mating sequence showed no tendency for females presentedlater to produce fewer females than those presented earlier.The data suggest that males can inseminate at least twice the numberof females that normally share a host with them. The breedingsystem of this species may be moving towards panmixis because ofrecent selection pressures caused by domestication of its primaryhost, the alfalfa leafcutting bee