We evaluated responses of protein-deprived and protein-fed mature (26–30-d-old) female melon flies, Bactrocera cucurbitae (Coquillett), to odor of host fruit and of proteinaceous baits by using 1 by 1 by 1-m cages containing nonhost plants. Protein-deprived and protein-fed females were attracted equally to odor of host fruit. For both types of females, odor of cucumber, Cucumis sativis L., and cantaloupe, Cucumis melo L., was more attractive than odor of tomato, Lycopersicon esculentum L. Odor of kabocha, Cucurbita maxima Duchesne, was more attractive than the odor of bittermelon, Momordica charantia L., but not more attractive than zucchini squash, Cucurbita pepo L. In choice tests, protein-fed females preferred cucumber odor over protein odor, whereas protein-deprived flies showed an almost identical response to the two odors. Our findings suggest that some feral host-seeking B. cucurbitae females that have fed recently on natural sources of protein and carry mature eggs might bypass proteinaceous baits, reducing the effectiveness of current approaches to melon fly management.