Ethological function of components of a sex attractant system for oriental fruit moth males,Grapholitha molesta (Lepidoptera: Tortricidae)

Abstract

Field studies of male Oriental fruit moth,Grapholitha molesta (Busck), behavior indicated that a mixture of cis-8-dodecenyl acetate (c8-12∶Ac) and ca. 7% trans-8-dodecenyl acetate (t8-12∶Ac) was requisite for upwind anemotaxis. The simultaneous emission of dodecyl alcohol (12∶OH) and the attractant blend of c8-12∶Ac containing ca. 7% t8-12∶Ac elicited a behavioral repertoire including close-range orientation, landing near the chemical source, wing fanning, and extrusion of the males' abdominal hairpencils in precopulatory display. The effect of 12∶OH in increasing trap catches was, therefore, not due to its effect on upwind anemotaxis, but rather to its importance in eliciting landing and other close-range precopulatory behavior. Interestingly, cis-8-dodecen-1-ol in extremely low ratios to the attractants (1∶333) appeared to duplicate the activity of 12∶OH used in ratios of 3∶1 to the attractants. Laboratory observations of mating sequences revealed that male hairpencil eversion always preceded copulation. The evidence supports a male response sequence based on specific component combinations and concentrations eliciting successive behavioral steps rather than a response hierarchy dependent on increases in concentration of a single chemical or blend. Additionally, the closeness of the males' approach to c8-12:Ac containing ca. 7% t8-12:Ac was optimal at a discrete emission rate, and male responses were diminished within 30–60 sec after the males' arrival at the attractant source.