There are still golden days left in the year. You know the ones.
The sun is warm enough to pleasantly tickle your skin and the breeze blows softly, hemmed with the only tiniest threat of winter.
Here in the east of England, summer is ending. The fens are beginning to accumulate more water. But for now, you can still hop over dips squelchy with rain and sidle round the muddy patches.
And it’s the perfect time to catch sight of the last of this season’s dragonflies.
From nymph to dragonfly
We have around 24 species of dragonflies and damselflies in the wet habitat of the fens in East Anglia. Dragonflies are bigger and flashier, resting with their wings open. Damselflies are more delicate and harder to spot, perching with folded wings.
We appreciate their beauty for about 5% of their lives, the majority of time being spent as nymphs maturing under water, shedding their skins periodically as they grow. They can live like this for up to five years, depending on the species, breathing through gills in their rectums.
Known as pretty fierce underwater predators despite their diminutive size, dragonfly nymphs propel themselves about by squirting water from the anus. Their lower jaws have sharp protrusions and, in a precision strike, the jaw darts forward to spear prey.
Finally, they mature, emerging from the water to peel away their last juvenile trappings.
Like a scene from a sci-fi movie, the skin on their backs split open and their adult dragonfly bodies emerge.
It takes a while for dragonflies to expand into their new shape, pumping insect blood — called haemolymph [US: hemolymph] — into their frames.
Their body temperature needs to reach 27 Celsius (80 Fahrenheit) to enable flight so they beat their wings together to warm up.
As you can imagine, this is their most vulnerable time. It’s estimated that half of all dragonflies eaten by predators at this point.
Adding to their sci-fi vibe, they are literally bug-eyed. It gives them a top-heavy look when they lean forward to perch. The eyes shine jewel-like as if they’re wearing a strange double-headed helmet.
As are typical of insects, dragonflies have compound eyes on the very top of their heads with many thousands of facets, up to 30000 in some cases. It is estimated that they use 80% of their brainpower to deal with the complex visual information they have to process.
They also have superb colour vision.
Whereas we mere humans have receptors in our eyes which distinguish three colours, dragonfly species have between eleven and thirty different colour receptors. They can see beyond our visible part of the electromagnetic spectrum and into the ultraviolet, allowing them to make visual distinctions that we can’t.
Aerial acrobatics with an ancient origin
Go back 300 million years and the familiar thrumming of proto-dragonflies would still assail your ears, albeit sometimes with a deeper sound.
Many textbooks, like the one I had as a child, show giant dragonflies — meganeura — with wingspans up to 70 centimetres (28 inches) in primeval forests. I try to imagine its weight bending the leaves of some ancient plant and the flush of air as the wings beat up and down.
Prehistoric dragonflies weren’t all as gigantic as this but well-preserved fossils of meganeura have been known since the 1880s. And indeed, they weren’t technically dragonflies yet. However, modern species retain many similar features such as the characteristic veiny patterns on their wings.
Dragonflies’ aerial agility — the seamless transitions between hovering and motion, the zig-zag zipping on the wing, the ability to fly backwards — are also due to this ancient heritage.
Unlike most modern insects whose wing muscles are connected within the thorax, dragonflies also have direct flight muscles. This means dragonflies can control each wing independently, giving them the fine control needed for their characteristic acrobatics.
Ethereal and ephemeral
The iridescent beauty of the adult dragonfly is short-lived. They have but two or three short months to fulfil their goal: to find a mate and breed.
Like so many animal species, the males are often highly colourful in bright blues, greens, reds, and yellows with striking black geometric shapes. The females, in contrast, are attired in subtler browns and yellows.
Mating is a bizarre business, though I suppose it isn’t strange at all if you’re a dragonfly.
It’s quite common to see a male and female locked in a curious circlet of copulation for many hours.
Look for loops of colour amongst the reeds or ropes or rushes by a channel of water and you might be able to spot them.
Once the female has accepted her mate, the tip of the male’s body latches on to the back of her head to keep her in place.
He moves sperm up to the top of his body, just below the head. The tip of the female curves round and latches there to receive the sperm to fertilise the eggs inside her.
When ready, the female will deposit her eggs (ovipositing) just at the surface of the water on bits of leaves, algae or soggy mud. I have sometimes seen females depositing on the wet edges of walkways or bridges but since these dry out, I doubt those eggs lasted very long.
The eggs, if they survive, will hatch in the light and warmth of the following spring and the resulting nymphs will mature underwater.
Survive and thrive?
With so many dragonfly species in our local environment — darters, hawkers, chasers — not to mention their damselfly relatives, it possible to spot dragonflies from mid-spring through to mid-autumn.
With our warming climate, the range of continental species is spreading, with the emperor dragonfly now being seen as far afield as Ireland and Scotland.
Globally, there are around 3600 species of dragonfly on every continent except Antarctica in habitats that abound with water from forests to marshes. The largest species alive today is the giant petaltail in Australia, which, as its name suggests, has little flaps on the tip of its body that look like petals. Its wingspan clocks in at an impressive 16 centimetres (6.5 inches).
The habitats dragonflies enjoy so much are becoming increasingly rare.
Conserving the places themselves plus keeping them free of harmful pollutants and human-caused algal blooms is critical. For instance, the orange-spotted emerald dragonfly hasn’t been seen in the UK since 1963 and was declared nationally extinct, due to river pollution, in 2008.
Locally at least, by virtue of protected habitats in nature reserves, common lands, and carefully planted parks and business landscapes, the story has some positivity. With a bit of effort and awareness, we can help our insect life prosper wherever we live.
We are lucky here. Our dragonflies and damselflies are thriving.
A quick hop and a skip from the city or business parks and you’ll find scores of wetland sanctuaries. While the weather is warm, you will very likely see the flamboyant flash of a dragonfly whizzing straight across your path.