THE RESPONSES OF PROSTEPHANUS-TRUNCATUS (COLEOPTERA, BOSTRICHIDAE) AND SITOPHILUS-ZEAMAIS (COLEOPTERA, CURCULIONIDAE) TO PHEROMONE AND SYNTHETIC MAIZE VOLATILES AS LURES IN CREVICE OR FLIGHT TRAPS

Flight traps and crevice traps for catching Prostephanus truncatus (Ho rn) and Sitophilus zeamais Motschulsky were studied in Kenya. The trap s were baited with pheromones of these beetles, with or without synthe tic maize volatiles. Ln the case of P. truncatus, which has a two comp onent pheromone consisting of Trunc-call 1 (T1) and Trunc-call 2 (T2), the components were tested singly or in a 1:1 combination. The additi on of synthetic maize volatiles to pheromone traps did not result in a n increase in trap catch of either S. zeamais or P. truncatus. The phe romone of S. zeamais was an effective lure in both crevice and flight traps but the actual numbers captured were low. Captures with traps ba ited for P. truncatus were much greater. The response of P. truncatus to the two components of its pheromone was affected by the type of tra p used. Crevice traps baited with either component alone caught fewer beetles than those baited with a mixture. in contrast, flight traps ba ited with T2 or the mixture were equally effective while traps with on ly T1 caught significantly fewer than either of these. These observati ons clarified apparent discrepancies between earlier studies in Tanzan ia and Mexico and are used to derive an hypothesis about the roles of T1 and T2; T2 appears to be a long-range attractant and T1 important f or modifying the response to T2 to facilitate close-range orientation. Adult P. truncatus arriving at the traps were sexed, and in both flig ht and crevice traps the majority of captures were females even though in the experimental maize cribs the beetles were present in a roughy equal sex ratio. The role of the pheromone is discussed in the light o f this observation.