The parasitoid fly Exorista japonica uses visual and olfactory cues to locate herbivore-infested plants

Females of Exorista japonica Townsend (Diptera: Tachinidae) are attracted to odors derived from corn plants (Zea mays L., Poaceae) infested by the larvae of Mythimna separata (Walker) (Lepidoptera: Noctuidae). We examined the effects of visual parameters on the olfactory attraction of females to host-infested plants. A paper plant model of one of four colors (blue, green, yellow, or red) was placed in front of a host-infested plant, which was hidden behind a mesh screen in a wind tunnel. The landing rate of females was significantly higher on the green plant model than on the other three models. When an achromatic plant model of one of four gray scales (white, light gray, dark gray, or black) was similarly tested, the response rate of females was higher toward the white model and decreased as the brightness of models decreased. Few female flies responded to the green plant model without odors of the host-infested plants in the wind tunnel. When the four color plant models were placed together in a cage filled with odors of host-infested plants, females remained significantly longer on the green model than on the other three models. These results showed that E. japonica females preferred the green color when odors of the host-infested plants were present and suggest that E. japonica uses visual as well as olfactory cues to locate the host habitat.