As soon as moth suitors pick up a whiff of female pheromone, the race is on. Only the fittest and first off the mark will have a chance of winning the girl and passing on his genes to the next generation. But, before keen males can take to the wing, they must warm their flight muscles to a specific temperature by shivering to ensure their optimal flight performance. So, what influence do moth females have on the race to win their favours? José Crespo, Franz Goller and Neil Vickers from the University of Utah, USA, wondered whether the female's potent pheromone cocktail might influence the male's pre-flight warm-up routine (p. 2203).
Placing chilled male moths downwind of an artificial pheromone blend in a wind tunnel, the team measured how long it took for the insects to start shivering, the total amount of time they spent shivering, their thoracic temperature at take off and the rate at which they warmed. Comparing the performances of the pheromone-exposed moths with those of moths that were down wind of other odours (individual pheromone components and other blends), Crespo and his colleagues saw that the pheromone-exposed moths began shivering earlier and took off sooner, even though their thoracic temperature was lower. And, when they measured the maximal vertical force produced by the insects' flight muscles over a range of temperatures (20–48°C), it was clear that the pheromone-stimulated moths' quick get away came at a price. Their muscles produced significantly less force at the lower take off temperature than moths that were slower off the mark and warmed up more, which could significantly compromise their flight performance.
The team says, ‘Our results shed light on thermoregulatory behaviour of unrestrained moths associated with the scramble competition for access to females and suggest ecological trade-offs between rapid flight initiation and sub-optimal flight performance’.