Acceleration

The lower male of the Small Redeye (Erythromma viridulum) pursuing the upper one is about 20 centimetres behind. To catch up, it increases its stroke movement compared to the pursued by wider flapping (120° instead of 80° like the upper male) and a higher stroke frequency (62.5 Hz instead of 54.5 Hz) and thus achieves a speed of 3.7 m/s instead of 2.2 m/s like the pursued.