not in Young In order to evaluate the rate of parasitism of alfalfa weevil Hypera postica (Gyllenhal) by its larval parasitoids, investigations were carried out in the experimental field of Agricultural Faculty of Tehran University (Karaj), during 1999-2002. Results showed that Bathyplectes curculionis (Thomson) was the most effective among the larval parasitoids for controlling its host population. The ability of producing two generations per year and such a high rate of activity that it could parasitize more than 36.3 percent of the host population at the time of pest outbreak are special advantages of this species. Although B. anurus (Thomson) parasitize in average 10% of its host population. due to univoltinity and low rate of parasitism, it is placed in the second order of importance. However the coincidence of its activity with the high level of the host population is a great advantage for this parasitoid. Oomyzus (=Tetrastichus) incertus (Ratzeburg) although parasitized up to 3! 0% of pest population in some cases, but its low rate of parasitism at whole (less than 15%) and lack of coincidence with the high population of the pest, put it in the third rank of importance. However the ability of producing more than three generations a year was the advantage of the latter wasp. BR Animals and man. Control. Biological control. Reproduction. Parasites diseases and disorders. Parasites. Insect parasites. Hosts. Insect hosts. Land zones. Palaearctic region. Eurasia. Asia. Hypera postica (Curculionidae): Host; Bathyplectes anurus (Ichneumonidae): Parasite; Bathyplectes curculionis (Ichneumonidae): Parasite; Oomyzus incertus (Eulophidae): Parasite. Bathyplectes anurus, Bathyplectes curculionis, Oomyzus incertus: Control of, Hypera postica (Coleoptera), Reproductive productivity, Coleopteran hosts, Hypera postica, Prevalence and control potential, Iran, Karaj; Hypera postica: Control by, Bathyplectes and Oomyzus (Hymenoptera), Hymenopteran parasites, Bathyplectes and Oomyzus, Prevalence and control potential, Iran, Karaj. ST Insecta, Coleoptera, Polyphaga, Curculionoidea, Curculionidae; Insecta, Hymenoptera, Apocrita, Terebrantia, Ichneumonoidea, Ichneumonidae; Insecta, Hymenoptera, Apocrita, Terebrantia, Chalcidoidea, Eulophidae. Arthropods; Beetles; Hymenopterans; Insects; Invertebrates. none