Calosoma sycophanta L. adults were fed either gypsy moth (Lymantria dispar L.) larvae or split grapes for set periods of time while their reproduction was monitored. Few female beetles reproduced unless fed gypsy moth larvae during the first week after they ended hibernation. Even females initially fed grapes that were later fed larvae had reduced reproduction. The implications these results have for relationships between beetle and gypsy moth populations are discussed.