Odour-mediated orientation behaviour of the lily beetle Lilioceris lilii

The lily beetle Lilioceris lilii (Scopoli) (Coleoptera: Chrysomelidae) feeds on Lilium, Fritillaria and Cardiocrinum plants and is a serious pest in gardens and amenity plantings in parts of Northern Europe and North America. In the present study, the odour-mediated behaviour of L. lilii is investigated by behavioural bioassays using a linear-track olfactometer. The behavioural responses of L. lilii to hosts and conspecifics are, at least in part, odour-mediated and the responses differ with respect to the physiological (reproductive) state of the adult beetle (i.e. pre- or post-diapause). Significantly more diapaused female L. lilii move into air streams containing the odour of intact host plants than into clean air, and move into air streams containing odour of host plants and beetles combined in preference to odour from manually-damaged host plants. Diapaused females also move into air streams containing odours from intact plants over those from larval-infested plants. Pre-diapause males move into the air streams of intact plants rather than L. lilii-infested plants. Pre-diapause females show no significant response in any experiment. The data indicate that the odour-mediated responses of L. lilii are consistent with those known for other chrysomelids that produce a male aggregation pheromone to which reproductive individuals of both sexes respond.