Effects of environmental temperature on pre-flight and flight activities in pheromone-stimulated male Helicoverpa zea

Male Helicoverpa zea moths orient and fly upwind in the presence of female pheromone. Prolonged flight is preceded by pre-flight shivering that ensures the endothermic flight muscles are sufficiently warm prior to take-off. This behavior depends on environmental conditions such as wind speed and ambient temperature. We previously showed that when sensing the attractive pheromone blend, male moths started to warm up earlier, took-off at lower thoracic temperatures and spent less time warming up than when exposed to incomplete pheromone blends. In the current study, we investigated the extent to which lower take-off temperatures of males, as well as changes in ambient temperature, affect their flight performance during pheromone tracking. In order to test this, we recorded the thoracic temperature of freely behaving H. zea male moths with a thermal-imaging camera and their subsequent flight tracks when orienting upwind towards a pheromone point source. The experiments were conducted in a wind tunnel with three distinct ambient temperatures: cold (19°C), room (22°C) and warm (26°C). At warmer temperatures, male moths needed less time to warm-up before taking flight, as was expected. Additionally, a higher percentage of these males successfully tracked the pheromone and arrived at the odor source. This finding indicates that ambient temperatures do not only determine the amount of time male moths need to spend warming up, but also influences their flight tracking abilities in plumes of attractive odor.

Acknowledgments: Supported by NSF IOS-1147233 to NJV, NSF DDIG IOS-1110836 to JGC and NIH DC06876 to FG.