Published online by Cambridge University Press: 10 July 2009
Responses of adult flea beetles Longitarsus jacobaeae (Waterhouse), to signals from ragwort plants (Senecio jacobaea Linnaeus) were studied by recording their directions of movement in a wind tunnel and their colonization of host-plants in the field. Starved beetle individuals, irrespective of gender, orientated toward upwind host-plants over a distance of 60 cm in the wind tunnel, whereas satiated beetles did not. In the absence of upwind host-plants, all beetles moved randomly in all directions, regardless of whether they were starved or satiated. Starved beetle individuals did not show directed movement towards hosts when plants were downwind in the wind tunnel, nor when in the presence of host-plants when the wind was absent. Groups of starved beetles orientated to upwind host-plants in the wind tunnel, as did individual beetles. In the field, plants over 60 cm upwind of the released beetles were found and colonized by more beetles than downwind plants, in spite of the presence of background vegetation. This confirms the result of laboratory experiments that L. jacobaeae can orient to upwind host-plants.