Correspondence between rates of host plant consumption and responses to the Acalymma vittatum male-produced aggregation pheromone

Abstract In field studies, wind-directed traps were used to investigate the resource-based properties of the male-produced aggregation pheromone of Acalymma vittatum (F.) (Coleoptera: Chrysomelidae). Responses to early season overwintered field-collected male A. vittatum without food were compared with those feeding on pollen, and in turn these were compared with those feeding on cucurbit seedlings. These comparisons were modelled after transitions as they would occur at the initiation of A. vittatum host plant colonization.
In another experiment, colony-reared male A. vittatum that had been fed only near isogenic lines of potted cucumber ( Cucumis sativus ) seedlings that either lacked or contained cucurbitacin were placed as bait in the traps. Using the inverse relationship, which is understood for A. vittatum , between previous exposure and the phagostimulant response to cucurbitacin, rates of foliage consumption could be manipulated. The interaction between relative rates of host plant consumption of the males used as lures and responses to the pheromone could thus be tested. The use of A. vittatum reared entirely without dietary cucurbitacin as bait also enabled evaluation of the potential role of cucurbitacin in pheromone biosynthesis. Trap responses were closely correlated with the rates of feeding of the beetles in the trap lures, but cucurbitacin was neither a precursor nor a prerequisite for the pheromone. Implications for early season field colonization and the adaptive significance of this pheromone are discussed.