Dragonfly flight: morphology, performance and behaviour

Odonata flight performance capabilities and behaviour and their body and wing form diversity are explored, and their interrelationships discussed theoretically and from observational evidence. Overall size and particularly wing loading appear predictably to be related to speed range. In Anisoptera at least, relatively short bodies and long wings should favour high speed manoeuvrability, though further information is needed. Medium and low aspect ratio wings are associated with gliding and soaring, but the significance of aspect ratio in flapping flight is less straightforward, and much depends on kinematics. Narrow wing bases, petiolation, basal vein fusion, distal concentration of area and a proximally positioned nodus - described by a newly defined variable, the "nodal index" - all allow high torsion between half-strokes and favour habitually slow flight, while broad wing bases are useful at higher speeds. The "basal complex" in all families seems to be a mechanism for automatic lowering of the trailing edge and maintenance of an effective angle of attack, but the relative merits of different configurations are not yet clear. There is serious need for more quantitative information on a wider range of species and families.