Visual stimuli and the response of female oriental fruit flies (Diptera : Tephritidae) to fruit-mimicking traps

Experiments were conducted to determine the response of female oriental fru it flies, Bactrocera dorsalis (Hendel), and 2 fruit fly parasitoids, Fopius arisanus (Sonan) and Diachasmimorpha longicaudata (Ashmead), to the color, shape, and size of visual sticky traps. Numbers of females captured on yel low spheres increased as sphere size increased with diameters of 5-11 cm. P reference of females for yellow spheres over green and red spheres was posi tively correlated with sphere size. Yellow-colored spheres and rectangular blocks of equivalent surface area were equally attractive to females; howev er, females were more attracted to red spheres than to red blocks of equiva lent surface area. The influence of background colors on the attractiveness of spheres was investigated by comparing the response of flies to 8 color combinations of the panels and spheres of Ladd traps. Standard Ladd traps, with red spheres attached to the center of yellow panels, captured more fem ales than any other trap tested and could be used to monitor populations of oriental fruit flies in orchards. Female oriental fruit flies may be attra cted to standard Ladd traps because of the visual contrast of red spheres a gainst a light background.