Rapid acceleration in Odonata flight: highly inclined and in-phase wing beating

Acceleration manoeuvres in free flight in nature of five damselfly (Zygoptera) and four dragonfly (Anisoptera) species were analysed by means of slow motion filming. Changes in stroke frequencies, stroke angles, stroke directions, angles of inclination of the wings, and the phase-relationship of fore- and hindwings were recorded during acceleration. Damselflies and dragonflies showed similar actions. In rapid acceleration, a shifting of the relationship of the two wing pairs to in-phase stroking and the use of highly inclined wings in the stroke direction opposite to the flight direction can be seen. Slow backward flight was done by phase-shifted stroking, fast backward flight by in-phase stroking. The downstrokes in slow and fast backward flight were quicker than the upstrokes. When fleeing from frogs, dragonflies show extreme flight action: all stroke phases were in-phase and the stroke phases directed toward the frog were very fast and highly inclined. Distances covered per stroke, non-dimensional flight velocities and acceleration are compared and discussed.