MALE SCENT IN LEPIDOPTERAN COMMUNICATION: THE ROLE OF MALE PHEROMONE IN MATING BEHAVIOUR OFPSEUDALETIA UNIPUNCTA(HAW.) (LEPIDOPTERA: NOCTUIDAE)

Abstract

Pseudaletia unipuncta (Haw.) males, experimentally deprived of hairpencils (male-specific scent organs), were less acceptable to females than were intact males. The degree to which females discriminated against males lacking hairpencils depended on the experimental protocol. When females were placed with males before scotophase onset, they tended to evade repeatedly and/or terminate genital contact with hairpencil-less males before eventually copulating, although this tendency was not statistically significant. When males were introduced after females had initiated calling, females refused hairpencil-less males significantly more often than intact ones. The incidence of copulation by hairpencil-less males was also lower than that of intact males, significantly so in one of the two populations tested. Neither copulation duration nor the dimensions of the cuticular portion of the spermatophore were correlated with the presence of hairpencils. Yet in all cases, females that mated with hairpencil-less males were more fecund and laid more fertile eggs than those mated to intact males. Hairpencil eversion could not be seen during courtship, nor did females show any obvious change in calling behaviour in response to scent from a freshly excised hairpencil. However, gas chromatographic analysis of hairpencils showed a decrease in titre of two scent components, acetic acid and benzaldehyde, just before the moment of genital contact between male and female, indicating that the pheromone was released at this time. These results suggest that P. unipuncta male pheromone facilitates female acceptance of males. The hypothesis that male pheromone carries information about the quality of a courting male is discussed in relation to recent work on arctiids, nymphalids, pierids and pyralids. An appendix of lepidopteran species possessing male scent structures is included.

Hairpencil Volatiles Influence Interspecific Courtship and Mating Between Two Related Moth Species

“…In Pseudaletia unipuncta Haworth, HP ablation caused a decrease in female acceptance of courting males (Fitzpatrick and McNeil, 1988). Female antennectomy or male HP ablation also significantly lowered mating success in courtship by the European corn borer, Ostrinia nubilalis Hübner (Lepidoptera: Pyralidae; Royer and McNeil, 1992).…”

“…In many species, HP volatiles have a clear effect on female behavior and influence the overall mating success of a courting male (Fitzpatrick and McNeil, 1988;Hillier and Vickers, 2004). In G. molesta, males 'flash' abdominal HPs directly in front of females that initiates short-range attraction (Baker and Cardé, 1979;Baker et al, 1981;Baker 1983).…”

Female sex pheromones in the host races and hybrids of the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae)

“…Mating in many insect species is modulated by sex pheromones, and in most cases females release long distance pheromones to attract potential mates (Cardé and Baker 1984) while male sex pheromones act at short distances during the final phase of courtship (Fitzpatrick and McNeil 1988;Birch et al 1990). Interspecifically, pheromones differ in composition and/or in the ratios of the constituent components, and these species-specific channels of communication have been seen as precopulatory reproductive isolating mechanisms to reduce inappropriate interspecific matings (e.g.…”

Are virgin male lepidopterans more successful in mate acquisition than previously mated individuals? A study of the European corn borer, Ostrinia nubilalis (Lepidoptera: Pyralidae)

“…In the true armyworm, Pseudaletia unipuncta, there is considerable interindividual variability in both the total quantity of male pheromone and the relative proportion found in the bilateral left and right abdominal hair pencils (Fitzpatrick et al 1985). Furthermore, after a mating sequence the male only loses about 6% of his pheromone (Fitzpatrick and McNeil 1988), which cannot be replaced. Thus, if at emergence a highquality male had twice the pheromone of low-quality one, then even after three matings, his pheromone titer would still exceed that of a poor-quality virgin.…”

“…Indeed, the rigorous selection process for obtaining experienced males in the mating trials (only 52 from an initial 200 met the requirements) may have inadvertently selected higher quality males. One way that females may assess the quality of potential mates is through male pheromones, as these may be of considerable importance for male mating success (e.g., Fitzpatrick and McNeil 1988;Birch et al 1990), including that of the ECB (Royer and McNeil 1992). In the true armyworm, Pseudaletia unipuncta, there is considerable interindividual variability in both the total quantity of male pheromone and the relative proportion found in the bilateral left and right abdominal hair pencils (Fitzpatrick et al 1985).…”