Host‐finding behaviour of Prostephanus truncatus (Horn) (Col., Bostrichidae): primary attraction or random attack?

Host‐finding behaviour of Prostephanus truncatus was evaluated in a four‐choice olfactometer for reactions to odours of maize, cassava chips, wheat, cowpea (a non‐host plant), and woody plant species in which reproduction has been observed, and of organisms associated with maize stores. P. truncatus reacted in general to odours from starchy commodities and to some of the woody plants. Beetles did not respond to volatiles from cowpea or organisms associated with maize stores, but did react to the aggregation pheromone produced by single male P. truncatus (secondary attraction). P. truncatus raised on cassava and emigrants from maize responded as strongly to maize odours as beetles raised on maize, whereas P. truncatus trapped with pheromone traps showed reduced or no reactions. Stored commodities seem to elicit short‐range arrestment, but not primary attraction at long range. However, stored products might only be attacked facultatively by P. truncatus, co‐evolved primary attraction could possibly exist to the native host‐plant complex.