Nature: The wonder of dragonfly wings have taken 300 million years to evolve, says Pam Taylor.

The British Dragonfly Society has just held its annual autumn meeting in Bristol. It was a really good conference full of interesting talks from both Britain and abroad. Most fascinating of all though was a talk about why dragonfly wing shapes are so diverse. Robin Wootton proposed a series of predictions based on differences in wing structure, before going on to test each prediction using real life examples.

First you have to understand there are huge differences in size between the largest and smallest species. The largest of the helicopter damselflies in Central America has a wingspan of 191mm. The smallest, a tiny damselfly with several common names including pinhead wisp, measures just 18mm across. Then there are differences between damselfly and dragonfly wing shapes. Damselfly wings tend to be broad near the tip, while dragonfly wings are broadest near the base. The narrow wing bases of damselflies means they fly relatively slowly. The wider wing bases of dragonflies allow faster flight because the wings are easier to flap.

All species have a flexible joint midway along the leading edge of each wing called the node. It has long been believed that the node aids efficient flight, but now we understand how. Use of high-speed photography, coupled with a knowledge of wing mechanics, explains this. Dragonfly wings aren't completely flat and the v-shaped leading edge of the wing inverts at the node. This, together with the arrangement of wing veins close to the thorax, holds each wing firm on the down-stroke, but allows the outer end of the wing to twist on the up-stroke. The closer the node to the body, the more twist that can be achieved, improving control and saving energy.

The short, broad wings of demoiselles have curved rather than straight veins. This holds their wings in a shallow cup-shape during flight and allows them to perform elaborate displays during the breeding season. The long wings and short bodies of fast agile species such as wandering glider, a pan-global dragonfly rarely recorded in Britain, allow it to fly long distances with ease. Dragonfly wing structure has changed little in over 300 million years, but these subtle differences between species allow for a great diversity of life-styles.