As it is national Dragonfly Week PETER FROST investigates these complex, intriguing and, at the same time, beautiful insects bequeathed to us by most distant prehistory.
“I saw, once, an endless procession, just over an area of water-lilies, of small sapphire dragonflies, a continuous play of blue gauze over the snowy flowers above the sun-glassy water. It was all confined, in true dragonfly fashion, to one small space. It was a continuous turning and returning, an endless darting, poising, striking and hovering, so swift that it was often lost in sunlight.”
That was Northamptonshire born novelist HE Bates writing in 1937 — in his series of nature essays Down the River — in what have been described as endless summers as dark war clouds gathered over Europe.
Bates would become much better known for his wartime books such as Fair Stood the Wind for France and after the war for his Darling Buds of May novella and sequels that became the hugely popular TV series.
While ambling beside your favourite canal towpath, riverside walk or village pond there’s nothing like the colourful, iridescent flash of a dragonfly to tell you that summer is here.
This is national Dragonfly Week and this Sunday July 23 there is a special dragonfly event at the National Trust’s Wicken Fen (below) in Cambridgeshire. You can join experts to learn more about some of our most spectacular wildlife.
There are 57 recorded species of Odonata in Britain, made up of 21 damselflies and 36 dragonflies.
Damselflies are smaller and weaker flying relatives of dragonflies.
So what is the main difference between a dragon and a damsel? The most noticeable is that most dragonflies rest with their wings open while damselflies rest with their wings folded together over their body. Damselflies are also weak fliers and tend to stay close to water.
The loss of garden ponds, concreting over the countryside and intensive farming has already lost us at least three species in the last 45 years and more are under threat.
The insects are also extremely sensitive to the weather and find it difficult to adapt to climate change.
The National Trust is so concerned about the issue that in 2009 it opened the UK’s first Dragonfly Centre at Wicken Fen in Cambridgeshire in order to create wetland habitats where rare species can be protected and studied.
Chris Packham — the often outspoken BBC Springwatch presenter — told us more species could be lost without action: “The loss of wetland habitat throughout the UK is having a massive impact on the long-term survival prospects for many dragonfly species.”
Adult dragonflies are amazing creatures with huge multifaceted compound eyes each made up of nearly 24,000 individual ommatidia or simple eyes.
They have two pairs of strong, transparent wings, sometimes with coloured patches, and an elongated often amazingly colourful and iridescent body. They are remarkably agile fliers.
Some of our native dragonflies are really large. In Britain some such as the Emperor and Brown Hawker reach a length of about 85mm (3.5in) and a wingspan of over 120 mm (5in).
Fossil evidence shows there were once dragonflies with wingspans up to about 750mm (30in). The first appeared between 250 and 300 million years ago and they have changed very little since then.
They are are fierce predators both in their aquatic larval stage — when they are known as nymphs or naiads — and as adults. Several years of their lives are spent as nymphs living in fresh water. The adults may be on the wing for just a few days or weeks.
They have a uniquely complex sex life involving indirect insemination, delayed fertilisation and sperm competition.
During mating, the male grasps the female at the back of the head or on the prothorax and the female curls her abdomen under her body to pick up sperm from the male’s secondary genitalia at the front of his abdomen.
Romantically the two curved bodies can form a heart shape while the actual coupling takes place.
Dragonflies are of some of the swiftest flying insects, with hawker dragonflies recorded at a top speed of over 20 miles an hour. They also display high manoeuvrability with some species capable of hovering and even flying backwards.
With their giant complex eyes dragonflies live in a world highly influenced by sight. The shape of those eyes allows them to see ahead, behind and to the side all at once. They also have great colour vision, which enables them to spot each other.
As well as the main two large eyes, they have three more located on the top of their heads in a triangle formation. These are simpler and detect very little detail and are specifically attuned to light intensity.
This ability allows the three eyes to detect information to assist flight, such as altitude and orientation while completing complex flight patterns.
Rather than being designed for walking dragonfly’s legs are positioned to catch prey in mid-air. Once a meal is trapped, the dragonfly’s forward facing legs are capable of holding up the prey item to its mandibles.
They eat small flying insects such as flies and mosquitoes — as well as butterflies and even smaller fellow dragonflies.
Their aquatic larvae are voracious, hunting various invertebrates, as well as tadpoles and even small fish. They alter their colouration between moults to blend in with their surrounding environment which helps them to stay hidden away from predators and prey too.
- Want to help our British dragonflies? Or just find out more about them? The British Dragonfly Society is the place to start. british-dragonflies.org.uk