Natural drones – dragonflies

Aeshna cyanea has stripes on a black abdomen.

GENERALLY interesting in its continuous wing flapping and hovering motions when airborne, the true beauty of a dragonfly is best displayed after it has alighted on a leaf or plant stem. Apart from butterflies, these mainly day-flying insects attract more public interest than any other insect group. The word ‘dragonfly’ only entered the English language in 1626.

Dragonflies belong to the order Odonata, meaning teeth, for they have very firm mandibles which gnaw through their prey before digestion. They are classified in the sub-order of Anisoptera, again a Greek word translated as ‘uneven wings’.

Eyeing a dragonfly at rest, one can readily notice that its hindwings are a bit broader than its forewings and with its long, slender body and large eyes, it is easy to see how these insects derived their English name, suggesting a reptile with wings!

Today there are just over 3,000 identified species of dragonfly in the world, with most found in tropical climes and very few species in temperate regions. The UK can boast only about 40 species.

It is conceivable that modern day hovercraft and high-tech drones were based on the dragonfly’s swift flying speed and hovering capabilities. In the 1950s the UK’s Royal Air Force flew a particularly lightweight helicopter known as the dragonfly.

Proto-dragonflies have been on Earth for at least 350 million years. Fossils of these have been identified in the Upper Carboniferous Coal Measures with wingspans of up to 750mm. These coal measures started as peat swamps in a tropical climate, not unlike today’s conditions in parts of Sarawak or Sabah.

Unravelling myths

As a youth, playing in countryside streams, I would often swish dragonflies away from my body. Why? I was frightened by their hovering movements and their two pincer-like claws at the ends of their long abdomens. Much mythology abounds on the perceived stings of dragonflies, especially on horses.

Over the centuries, in various English dialects, dragonflies have been labelled adderbolts, horse-adders, horse-stingers, and the devils-needles. The real truth lies in the fact that horses, like all animals, sweat in hot weather, attracting flies which in turn provide dragonflies with plentiful food! Even today, in my rural location, I have heard farmers telling their children, “Beware, for that dragonfly will sting you!”

Absolute rubbish, for I’ve had British and Malaysian dragonflies settling on my hands and arms and can feel their mandibles gently scratching at my dead skin. Possibly, it is because of a dragonfly’s long, slender abdomen with striking colourations on each of its 10 segments and its fork-like clasps that has confused folk with snakes.

In the wider world

With the exception of Antarctica, these insects are found on all continents. One species, the globe skimmer (Pantala flavescens) lives in all warmer areas while only one species, the tree emerald, has been recorded within the Arctic Circle.

There are some species that prefer acidic or alkaline peat swamp conditions but most dragonflies prefer living near neutral pH water, in ponds and especially alongside rivers.

Whilst essentially waterside insects, I have seen them settling on garden plants in Kuching and the UK. The largest dragonflies I have ever seen have been settling on lotus plants in the Seychelles, Cambodia and Myanmar. All dragonflies settle on vegetation with wings open in a horizontal position and should not be confused with damsel flies that fold their wings against their bodies.

Anax imperator is metallic blue. – Photos by Böhringer Friedrich

Lifestyle and diet

Whilst we all admire the delicate patterns on their wings and their multi-coloured abdomens, there is much more to these insects than the naked eye can behold.

Their two large compound, global vision eyes and their two antennae, which serve as sensors for landing and direction, may be spotted. Their tongues flick in and out, trapping insects for their mandibles to dissect.

It is the thorax of a dragonfly that holds its wings, together with its three pairs of legs, used for catching and holding its prey or to clasp onto a plant with its claws. The abdomen contains a penis or an ovipositor.

I shall not disclose the erotic behaviour of the dragonflies when mating but suffice to say a female will lay a clutch of over 1,000 eggs on floating vegetation.

Within a week, these hatch into wingless nymphs with extendable tongues which shoot in and out to catch other insects such as mosquito larvae and even tadpoles.

With internal gills, they can pump water in and out of their bodies and can use this method for propulsion in jet form.

The nymph’s metamorphosis into adulthood usually occurs at night and, as its tissues are still soft, it climbs up a reed to allow its exoskeleton to harden as it breathes its first air.

This intake allows its wings to open and develop. Some dragonflies can fly at an average speed of 12.5 metres per second, approximately 100 times their body-length and, when retreating backwards, at three lengths per second. In temperate regions their lifespans are approximately six to seven months.

Carnivorous by nature, they feed on midges, mosquitoes, butterflies, moths and even on smaller species of dragonfly. Consuming up to 20 per cent of its body weight daily, a dragonfly rarely goes hungry.

British dragonflies

Sadly, many species peculiar to Britain have disappeared over the years owing to land reclamation and drainage of natural wetland areas, with three species recorded as extinct in 2000.

Yet, with climate change, other migrant species have been recorded, to include North African dragonflies.

I can only positively recognise two British species. The Southern Hawker (Aeshna cyanea) with its black abdomen crossed with white stripes, yellow flags, and brownish speckles is mostly found in hedgerows.

The most common species is the Emperor Dragonfly (Anax imperator) with its beautiful metallic light blue-edged abdomen and a central brownish-black streak throughout.

Bornean dragonflies

A regular visitor to Sarawak is the Canadian born, wildlife conservationist and naturalist Ronald Orenstein, who has highlighted two local species of dragonfly in Sarawak.

He has spotted the local (Orthetrum sabina) at Damai Beach, and the Coastal Glider (Macrodiplax cora). Further details may be acquired from his website at the end of this article.

Actually, 400 species of dragonflies have been recorded in Malaysia and yet more remain to be identified as Odanata species.

Frankly, with the ever decreasing rainforest habitats in many tropical regions, it is likely that many as yet, unknown species of dragonfly will become extinct even before they are identified and named.

Threats

Natural predators include raptors, swifts, swallows and flycatchers, together with wasps. At their larval stages of the dragonfly’s development, ducks, herons, fish, frogs, newts and water spiders feast well on them.

There are also worm and bacterial infestations. Anthropogenic threats have gradually reduced worldwide populations through man-induced climate change, air pollution, and the overuse of pesticides and spraying of field crops.

Interestingly, dragonflies, like ducks, act as natural pest controls in lowland rice fields, thus enhancing farmers’ harvests.

Do marvel at the movements and colourations of these majestic insects in your gardens, parks or fields.

The intricacy of their vein-like wing structures are marvels of nature and do, always, remember that dragonflies have been on Earth long before mankind appeared. Further research still needs to be done on Malaysian species – a chance for enquiring conservationists and research students?

For Sarawak dragonflies do visit www.ronorenstein@blogspot.co.uk.

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