An investigation into the potential of adaptive signal modifications and air movement communication during agonistic encounters between crickets Gryllus bimaculatus

This study involves two investigations on the signalling behaviour of Mediterranean field crickets Gryllus bimaculatus during agonistic encounters. The first investigation examines the possibility that crickets modify their signalling in varying environments, to increase signal efficacy. Agonistic encounters between male crickets were staged in the light and the dark. The results found a longer antennal fencing duration in the dark, suggesting the crickets were modifying their signalling to reduce contest costs in instances of decreased signal efficacy. To probe whether or not the difference in antennal fencing duration was an active signal modification, contests between blind and seeing crickets were staged. The findings indicated antennal fencing is a visual signal that is ineffective in influencing receiver behaviour when visual cues are absent. Therefore, rather than being an active signal modification in response to a perceived reduction in visual signal efficacy, the results strongly suggest that signal form is modified as a direct result of its lack of effect on the receivers behaviour. Many arthropods possess filiform hair sensilla, which are extremely sensitive air movement detectors, hence the second study investigated whether crickets are using air movement signals during agonistic encounters. Contests were staged between pairs of male crickets, either with their cerci intact, or ablated. It was predicted that if a component of the antennal fencing signal is received as air movement, the manipulations should impair signal reception and alter contest duration and escalation frequency. The results found no difference in contest behaviour between the cerci intact and cerci ablated groups. To ensure that visual signals were not maintaining signal efficacy, the experiment was repeated under complete darkness. There was no change in contest behaviour, indicating that air movement signals are not used in agonistic encounters between crickets.