Responses of Diadegma semiclausum, a specialist solitary parasitoid of diamondback moth (Plutella xylostella) larvae, to host-infested cabbage plants were studied. Females were more attracted to host-infested plants than uninfested plants in a wind tunnel. The origin of the attraction was neither the hosts nor their associated products, such as feces, silk and exuviae, but the infested plant itself. Once on the infested plant, the females initiated specific antennal contact with a host-damaged site on a leaf to search for hosts. Based on these data, the effect of chemical cues from infested plants on host searching by females is discussed.