Lanceleaf crotalaria, Crotalaria lanceolata E. Mey (Leguminosae) was found hosting the small green stink bug, Piezodorus guildinii (Westwood), in Paraná State, Brazil. In the laboratory, nymphs showed less mortality when fed on immature pods of crotalaria (64%) than when fed on immature pods of soybean, Glycine max (L.) Merrill (88%). From 2nd stadium to adult, nymphs required less time to complete development on crotalaria (mean of females and males = 18.4 days) than on soybean (21.5 days). Fresh body weight at adult emergence was greater on crotalaria (mean of females and males = 51.4 mg) than on soybean (42.2 mg). Adult P. guildinii tended to live longer on crotalaria than on soybean. Mean adult longevity was 34.6 days on crotalaria, and 28.8 days on soybean. However, the reproductive performance of females, although similar on both foods, tended to be greater on soybean. These results indicated that P. guildinii was able to develop and reproduce on the wild host lanceleaf crotalaria. Compared to soybean, this weed plant was more suitable for nymph development, and equally suitable for adult reproduction.