Responses of Wild and Laboratory-cultured Dacus oleae1 to Host Plant Color

Abstract

To the human eye, the silvery color of the bottom leaf surface renders olive tree foliage readily distinguishable from the foliage of other trees in the same habitat. We assessed the responses of wild and laboratory-cultured olive flies, Dacus oleae (Gmelin), to large vertical rectangles erected in an open field and displaying, 2-dimensionally, various leaf and painted surfaces. Both fly types clearly distinguished real foliage from clear Plexiglas,® but neither type was more attracted toward the foliage of its only known host, olive, than toward fig foliage. In fact, fewer flies of both types flew toward the bottom surface of olive leaves or a mixture of top and bottom olive leaf surfaces than toward either surface of fig leaves or the top surface of olive leaves. Also, fewer flew toward a paint approximating the spectral reflectance of the bottom surface of olive leaves than toward a paint approximating the reflectance of the top surface of olive leaves. Evidence indicates that these responses were to treatment color and were not detectably influenced by leaf pattern or odor.