Responses of carrot fly larvae, Psila rosae, to the odorous and contact-chemostimulatory metabolites of host and non-host plants

ABSTRACT. The responses of third instar carrot fly larvae, Psila rosae , to plant metabolites were studied in a moving air olfactometer. Directed responses over distances greater than 7.5 cm were obtained to both host and non-host plant odours, to CO₂ and methyl eugenol, a volatile secondary metabolite of carrot roots. Larvae also oriented to gradients of contact-chemostimuli. The role of both olfactory and contact-chemostimuli in the host plant finding behaviour of P. rosae larvae is discussed, and observational evidence for the behavioural mechanisms involved presented.