The wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae) was first found in wild grasses and soon became an economically important pest of wheat after cultivation began in the northern Great Plains. Of the species of parasitoids that attack C. cinctus in wild grasses, only Bracon cephi (Gahan) and B. lissogaster Muesebeck (Hymenoptera: Braconidae) have been found in wheat. Levels of parasitism vary between wheat-producing regions in Montana. Parasitism levels were increased by releasing individuals from a region with high levels of parasitism into a region where parasitism levels were low. This suggests that there has been unequal rates of parasitoid adaptation from wild grasses to wheat in different regions of Montana.