Olfactory modulation of pre-flight shivering behavior in male moths

In nocturnal moths olfaction is the predominant sensory modality shaping many of the adult animal?s activities, including reproduction. A two-component pheromone blend is sufficient to elicit the typical zigzag upwind flight behavior in Helicoverpa zea males. However, before flight can be initiated, the endothermic flight muscles must first be warmed-up by shivering. We investigated the influence of olfactory sensory input on this thermoregulatory behavior. An infrared camera placed above a small wind tunnel was used to record and measure the thoracic temperature changes in free animals that were exposed to odor blends varying in their composition (ranging from an attractive pheromone blend to an unattractive blend containing behaviorally antagonistic odorants). In addition, maximum vertical force per unit muscle mass as a function of thoracic temperature was determined in tethered flight with a force transducer. Male H. zea exposed to the attractive pheromone blend spent less time on the ground when shivering, warmed up at faster rates and took off at lower mean thoracic temperatures than those males exposed to other pheromone blend combinations. Force measurements demonstrated that these lower thoracic temperatures exhibited by males exposed to the attractive pheromone blend, correspond to low maximum vertical force production when compared to the other treatments. Since there is an optimal thoracic temperature for flight, these results indicate that male moths are prepared to compromise optimal flight efficiency with the possibility of being the first to arrive at a receptive female. 2. Introduction Attractive, unattractive and even repulsive scents are environmental cues that allow animals to assess the presence of a particular resource (e.g., food or mates) and how they will react to it. Strong selective pressures act on this olfactory behavior which includes the decision of whether or not to approach the olfactory stimulus and an efficient and successful location of the source. How olfactory stimuli influence motor behavior is an important question of sensory motor integration. In this study, we investigated the warm-up behavior of the moth Helicoverpa zea when sensing different odors based on pheromone blends.