Season, sex and flight muscle investment affect take-off performance in the hibernating small tortoiseshell butterfly Aglais urticae (Lepidoptera: Nymphalidae)

Flight ability is generally expected to increase with relative flight muscle mass. Changes in weight can therefore be expected to influence the capacity to rapidly take-off, which can determine mating success and predator avoidance. This study examined the influence of relative flight muscle mass, sex, and season on free take-off flight ability in a butterfly model (Aglais urticae) that undergoes adult winter hibernation. Mass change and take-off flight ability (velocity and take-off angle), was predicted to fluctuate with season (before, during and after hibernation) and sex (due to reproductive investment). Our results indeed showed changes in take-off ability in relation to both parameters. Females maintained velocity across seasons but reduced take-off angles during and after hibernation. Male flight speed increased during and after hibernation, whereas take-off angles were significantly reduced during hibernation. Finally, we showed that investment in relative flight muscle mass increased velocity in female, but not in male butterflies.