Matutinal mating in Aeshna grandis and A. viridis – a behavioural pair of twins prefers early-morning sex (Odonata: Aeshnidae)

We investigated the hitherto unknown matutinal mating behaviour of Aeshna grandis and found that matings basically occurred at dawn. With the first morning light males began performing a searching flight for females that roosted deep in terrestrial vegetation characterized by reed, rush and grass. Matutinal mating in the distinctive twisted wheel position is documented. Twisted wheels are unique as they are not formed in flight but while perching on vegetation and they show no readiness to escape. The twisted position, with the male hanging upside down and his appendages being obliquely slipped across the female’s head, is the result of the formation of mating wheels with the female perched. Later in the morning we observed feeding flight at suitable sites and resting in low vegetation of a wet meadow. During this resting phase some males inspected the vegetation on the wing, described here as ‘mid-morning searching flight’. In this situation and also when foraging individuals aggregated, we found untwisted, upright hanging couples, which we interpret as wheels formed in flight – an indication of alternative mating tactics. Aeshna viridis, also known to exhibit matutinal matings, occurred syntopically and behaved similarly. We interpret the energy-sapping searching flight at dawn as sexual selection: females select genetic quality by choosing only the fittest mates.

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