Male moth sensitivity to multicomponent pheromones: Critical role of female-released blend in determining the functional role of components and active space of the pheromone

Abstract

In the present study male redbanded leafroller (Argyrotaenia velutinana), cabbage looper (Trichoplusia ni), and Oriental fruit moths, (Grapholita molesta), were tested in a flight tunnel to (1) the major pheromone component, (2) theZ/E pheromone component mixtures for Oriental fruit moth and redbanded leafroller, (3) and the female-released blends, over a series of dosages. Experiments were designed to test the hypothesis that male response downwind of a female is initiated by the major component and that minor components function only to elicit behaviors close to the female during close-range approach and courtship. The results did not support this hypothesis, but rather showed that males initiated upwind flight in significantly higher percentages to the complete blends of components, at all dosages, compared to single components or partial blends. Addition of minor components also signficantly enhanced male perception of the major component at lower dosages, resulting in completed flights to dosages of the major component that alone did not elicit any upwind flight. Our results support the concept that minor components function to enhance male sensitivity to the pheromone, and the specificity of the signal. Our results also support the hypothesis that the active space of the pheromone is a function of the upper and lower concentration thresholds for the blend of components, and not simply for the major component.

Calling behaviour and male response towards sex pheromone of poplar moth Condylorrhiza vestigialis (Lepidoptera: Crambidae)

“…This has been studied in detail with respect to lepidopteran sex pheromones. Species-speciWc communication within the phylogenetic groups with only a few, structurally similar, compounds is enabled by pheromone synergists and antagonists, which function to enhance and to inhibit, respectively, the behavioural response to the main pheromone component (Linn et al 1986;Witzgall et al 1996;Cardé and Minks 1997;Arn et al 2000). This unique GC-EAD active peak detected in C. vestigialis gland extract is probably the main pheromone component, and further studies on structural identiWcation will verify the existence of possible minor pheromone components.…”

Analysis of chemical signals by nervous systems.

“…Our neurophysiological studies have focused on three important properties of the sex-pheromonal signal: its quality (chemical composition of the blend), quantity (concentrations of components), and intermittency [owing to the fact that the pheromone in the plume downwind from the source exists in filaments and blobs of odor-bearing air interspersed with clean air (47,48) (49), and when the pheromone blend stimulates his antennae intermittently (39,50). In our studies, we examine how each of these important aspects of the odor stimulus affects the activity of neurons at various levels in the olfactory pathway.…”

Codling moth males do not discriminate between pheromone and a pheromone/antagonist blend during upwind flight

“…Species-specific communication within phylogenetic groups with only a few, structurally similar, compounds is enabled by pheromone synergists and antagonists, which function to enhance and to inhibit, respectively, the behavioural response to the main pheromone component. Compounds which synergize the response of conspecific males often have an antagonistic effect on the response of heterospecific males, and the same compound may act either as synergist or as antagonist in the same species, at different blend ratios (Linn et al 1986;Witzgall et al 1996;Arn et al 2000).…”