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Examines the effects of different hosts and presence of conspecific females on male produced aggregation pheromone of beetles, Rhyzopertha dominica. Signal modification; Phenotypic plasticity of Rhyzopertha dominica; Pheromone signalling.

Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) is a sporadic, but serious pest of maize and cassava in the tropics. Farmers report that some years are far worse for damage than others and it is also known that the numbers of insects dispersing, as measured in pheromone traps, varies between years. Using purpose-built mini-stores it was shown that flight-trap catches of P. truncatus were a significant predictor of the risk of stores becoming infested in Ghana but not Tanzania. The estimated relationship between these two variables was, however, similar in both countries, and also matched data subsequently obtained from observations of farmers’ stores in Ghana. These findings are an important step towards the development of a warning system to decrease the uncertainty of P. truncatus threat to stored maize and cassava. [Copyright &y& Elsevier]

Intermale variation in pheromone signaling has been confirmed and quantified by measurements of pheromone produced by single adult male Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae). Males varied in both the amounts of the two components of their aggregation pheromone and the ratio of one component to the other. The mean rates of production of the pheromone components TI and T2 were 1.9 and 0.5 µg/day, respectively. There were repeatable differences among males in the amounts of T2 produced and the proportion of T1 in the pheromone blend over two weeks. Of the 15 males studied, one released a large burst of pheromone in a short period, while the remainder, if they did release, did so over an extended period. This suggested that there may be two alternative release strategies and the significance of this is discussed. [ABSTRACT FROM AUTHOR]