In order to study biology and seasonal parasitism of alfalfa weevil, Hypera postica by Bathyplectes spp. wasps, alfalfa fields were visited weekly and sampling was done by a sweep net (30 cm in diameter) in Chahar Mahal Va Bakhtiari province in 1997 to 1999. Bathyplectes curculionis Thomson and B. anurus Thomson were collected from alfalfa fields. B. anurus was the dominant species. In Shahre-Kord climatic conditions adult alfalfa weevil overwintered in soil and litter. Adults of B. anurus emerge from overwintered cocoons in the spring and prefer to parasitize third and fourth instars larvae of alfalfa weevil. One parasite consumes a single H. postica larva and ultimately emerges to spin a white-banded, dark brown cocoon, usually inside the weevils own, netlike cocoon, and enters diapause until the fall. After pupation, it changes into adult and remains in diapause in the cocoon until the next spring. Maximum and minimum percentage parasitism in 1998 were 63.5% in Dezak area and 1.25% in Ardal area, respectively and also in 1999 were 57% in Boldagi and 9.8% in Juneghan area respectivly. Results showed that both H. postica and B. anurus were univoltine in Shahre-Kord region. Life cycle and development; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Land zones; Palaearctic region; Eurasia; Asia Hypera postica (Curculionidae); Hymenopteran parasites; Bathyplectes anarus; Parasite biology & seasonal prevalence; Plant hosts; Medicago sativa; Iran; Chahar Mahal Va Bakhtiari province; Hymenopteran parasite biology & seasonal prevalence Bathyplectes anarus (Ichneumonidae); Life cycle; Coleopteran hosts; Hypera postica; Parasite biology & seasonal prevalence; Iran; Chahar Mahal Va Bakhtiari province; Biology & seasonal prevalence in coleopteran host none