The magnificent flying machine

A DRAGONFLY has eyes so large that they cover most of the insects head. In common with other insects, it has compound eyes made up of many hexagonal facets, each containing a tiny lens. The iridescent eyes of the dragonfly are composed of thousands of facets, ranging from 10,000 to 30,000 depending on the species.

It has been theorised that each of these tiny lenses records a small fragment of the scene, and the insect sees the entire image as a mosaic. This is the mosaic theory of insect vision first expounded by German physiologist Johannes Peter Müller in 1829.

And the dragonfly has such large eyes the better to see. Scientists believe that it has the best eyesight among insects. The highly convex shape of the eyes gives this insect a very wide angle of vision. Because of its good eyesight, a dragonfly can hunt until very late into the evening.

The dragonfly’s head is also extremely moveable, a further aid to vision. The insect can turn its head sideways, and move it backwards, forwards and downwards. If you have the opportunity, observe a dragonfly perched on a twig or a leaf, waiting for an insect prey to fly within striking range. You will see that it constantly moves its head to survey its surroundings.

Good eyesight is not the only attribute of this entomophagous hunter (meaning it eats other insects). It is a fast flier and capable of some very impressive aerobatic manoeuvres. A member of the larger species can fly at speeds of nearly 100kph (60mph). It can hover like a helicopter, maintaining its mid-air position with consummate skill, its diaphanous wings glinting in the sunlight. It can fly vertically. It can stop or turn sharply in the midst or rapid flight. It can even fly backwards. It is the magnificent flying machine that no man has yet invented.

Being such an accomplished flyer, a dragonfly can easily snatch its prey in flight. It begins tearing up its prey while still flying, and returns to its perch to finish the meal. With its acute vision, extraordinary flight capability and voracious appetite, a dragonfly is among the most fearsome predators in the insect world.

(This article was published in the December 1996 issue of Journal One.)