Evolution of the Sex Pheromone Communication System in Ostrinia Moths

It remains a conundrum in the evolution of sexual communication how the signals and responses can co-ordinate the changes during speciation. The genus Ostrinia contains several closely related species as well as distinctive strains with pheromone polymorphism and represents an example of ongoing speciation. Extensive studies in the genus, especially in the species the European corn borer O. nubilalis (ECB), the Asian corn borer O. furnacalis (ACB) and the adzuki bean borer O. scapulalis (ABB), have provided valuable insights into the evolution of sex pheromone communication. This review presents a comprehensive overview of the research on pheromone communication in different Ostrinia species over the past four decades, including pheromone identification and biosynthesis, the ligand profiles of pheromone receptor (PR) genes, the physiology of peripheral olfactory sensory neurons (OSNs) and the projection pattern to the antennal lobe. By integrating and comparing the closely related Ostrinia species and strains, it provides an evolutionary perspective on the sex pheromone communication in moths in general and also outlines the outstanding questions that await to be elucidated by future studies.

Sexual attractiveness and reproductive performance in ageing females of a coccoid insect

Female age strongly influences reproductive success in various animals. Males are, therefore, expected to show preferential responses to sexual signals released from females of ages suitable for reproduction. Here, however, we report an unexpected and contradictory effect of ageing on sexual attractiveness and reproductive performance in a coccoid insect: the pheromone-based attractiveness of females increased with ageing, though their reproductive performance was in rapid decline. Surprisingly, senescent females continued releasing relatively high amounts of pheromone and maintained their sexual attractiveness, even at ages when they had almost completely lost fertility, with reduced densities of endosymbionts to support their physiology. Our dataset suggests a potential sexual conflict within a pheromone communication system, where females benefit at males' expense through deceptive signals of fertility.

Modification of the sex-pheromone communication system associated with organophosphorus-insecticide resistance in the obliquebanded leafroller (Lepidoptera: Tortricidae)

The pheromone communication systems of azinphosmethyl-susceptible (susceptible) and azinphosmethyl-resistant (resistant) obliquebanded leafrollers, Choristoneura rosaceana (Harris), from the Niagara Peninsula of Ontario, were compared in the laboratory and field. The pheromone glands of resistant females contained approximately one-half as much (Z)-11-tetradecenyl acetate (Z11-14:Ac), (Z)-11-tetradecenol (Z11-14:OH), and (Z)-11-tetradecenal (Z11-14:Al) as the glands of susceptible females. A similar amount of (E)-11-tetradecenyl acetate (E11-14:Ac) was found in the glands of the two types of females. The pheromone effluvium from resistant females contained approximately one-half as much Z11-14:Ac, E11-14:Ac, Z11-14:OH, and Z11-14:Al as the effluvium from susceptible females. The onset and duration of female calling and the effect of age on calling were similar in susceptible and resistant C. rosaceana. In an apple orchard, traps baited with resistant females captured approximately one-half as many marked and released susceptible and resistant males as traps baited with susceptible females. There was no difference in the response of antennae from susceptible and resistant males to synthetic Z11-14:Ac and E11-14:Ac. The antennae of resistant males were less sensitive to Z11-14:OH and Z11-14:Al than the antennae of susceptible males. In a flight tunnel, pheromone-gland extracts from susceptible and resistant females, and calling susceptible and resistant females, were equally attractive to both susceptible and resistant males. In an apple orchard, the rate of capture of marked and released susceptible males was greater than that of resistant males in traps baited with susceptible females, but not in traps baited with resistant females or in traps baited with synthetic pheromone. The reduced ability to locate virgin females suggests that the presence of resistant males in an apple orchard may result in a reduction in the capture of moths in pheromone-baited traps. The reduction in trap catch was likely not caused by resistant females because they were less attractive to males than susceptible females and would therefore, in theory, compete less with traps for males than susceptible females. The differences observed in the pheromone communication systems of susceptible and resistant C. rosaceana are likely pleotropic effects associated with the selection for insecticide resistance.