Submitted to: Journal of Entomological Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 24, 1997
Publication Date: N/A
Interpretive Summary: We wished to know about fundamental aspects of how insects respond to their sex pheromone. This type of knowledge is limited and it could eventually help us to design strategies to use pheromone in manipulation of insect behavior to our advantage. To expand our knowledge of manner in which the European corn borer responds behaviorally to its sex pheromone, we conducted a test to find if the way pheromone was presented to males would change they way they respond to it. Tests showed that when males were exposed to pheromone in groups they responded significantly more competitively toward pheromone, on a per-male basis, than did males shown pheromone individually. It seems that males in groups somehow sense the presence of cohorts and are stimulated to a higher level of sexual competitiveness than singlet males. When male gangs are pursuing a relatively limited female resource, it would make good sense from an evolutionary viewpoint to be as competitive as possible. Intraspecific male competition should ensure that the most fit male will get a mate and maintain his genetic complement in the population. Observation of this adaptive behavior provides fundamental insight into an evolutionary aspect of the European corn borer sex pheromone communication system. The study also proved that the way an insect responds to a chemical stimulus is dependent upon the context in which it is presented.
The context in which female sex pheromone was presented to European corn borer males influenced the apparent sexual aggressiveness of males toward the pheromone stimulus. When groups of four males were simultaneously exposed to female sex pheromone in a wind tunnel, they responded, on a per-male basis, significantly more intensely with hovering behavior within 3 cm of the pheromone source than did comparable males presented pheromone singly. This was true whether adult males were caged in groups or as single males in isolation for 3-5 days before exposure to pheromone. Males held in isolation before pheromone exposure, whether tested singly or in groups of four flew upwind in the pheromone plume and landed on the pheromone source significantly more often than males that were caged in groups. The results show that the behavioral response of an insect to a chemical stimulus is dependent upon the context in which it is presented and that applying the concept of contextual chemical ecology can provide evolutionary insight into the adaptive value of certain behavior.