Only about 1% ofBathyplectes anurus(Thomson) females, from five locations in three states, had nonfunctional ovaries. In contrast, the ovaries of nearly 10% ofB. curculionisfemales from four states were infertile. This infertility was related to time of emergence from the cocoon; females emerging during the first half of the emergence period had normal ovaries, but 23% of late-emerging females had nonfunctioning ovaries. Ovaries of both species reached maximum fertility (presence of eggs in oviducts) within 24 h of eclosion. Cocoons that had previously been candled, to eliminate dead individuals, had eventual survival rates of from 54% (B. curculionis) to 68% (B. anurus). The proportion of females produced was 49% forB. anurusand 63% forB. curculionis. The reduced ovarian function ofB. curculionisis one of the likely reasons thatB. anurushas become the dominant parasite of alfalfa weevil larvae in the New Jersey-southeastern Pennsylvania area during the past decade.