Two nabid species,Nabis roseipennisReuter andN. americoferus(Carayon), were collected from alfalfa fields in Indiana in 1988 and 1989. Body weights and numbers of eggs at dissection were recorded and compared within and between species by location and time. The numbers of eggs at dissection were regressed on body weight, and compared between species. Overall,N. roseipenniswere found to weigh more thanN. americoferus. N. americoferusappeared to have a minimum weight threshold for egg production. No such threshold was evident forN. roseipennis. Egg-to-weight relationships suggested thatN. americoferuswas more efficient at producing eggs thanN. roseipennis,which helped to explain interspecific comparisons of fecundity. The findings of the study are compared to similar studies of nabid reproduction and related to the potential use of nabids in pest management.