The Oldest Hunter in the Garden

Dragonflies were mastering flight three hundred million years before the first bird. They hunt with incredible precision, live most of their lives unseen underwater, and one of them holds the record for the longest migration of any insect on earth. They are also a living verdict on the health of your water, and one of the very few wild wonders you can summon to your own patch by digging a simple pond with shallow margins and a few plants.

A dragonfly hangs in the air at the edge of our pond on a warm afternoon or divebombs for insects through the air on a summer night - in alarming quantities in my garden this year!

The dragonfly is the most quietly astonishing animals on the planet, and almost everything that is true about it is hidden from the person watching. Its deep past, its double life, its lethal skill, its record-breaking travels, and the verdict it silently passes on your water are all invisible in that idle, shimmering moment.

Older than almost everything

Let's start with time, because the scale of it reframes everything else.

Dragonflies belong to one of the most ancient lineages of flying insects on earth, going back more than three hundred million years, long before the dinosaurs, before birds, before flowering plants existed at all. When you watch a dragonfly hunt, you are watching an insect older than almost every other living thing.

In the Carboniferous, that lineage produced the largest insects that have ever lived, the griffinflies, whose best-known member, Meganeura, had a wingspan approaching seventy centimetres, (closer to a crow than a garden insect).

They could grow so vast because the atmosphere of that swampy, forested world held far more oxygen than ours does, enough to feed a giant body through the simple tube-based breathing that limits insect size today. The giants are long gone, but the basic design proved so good that it barely needed changing. The dragonfly at your pond is running ancient software that evolution has scarcely had reason to update.

Two lives, and the one we never see

I remember being shocked to discover as I learned more about insect life cycles on my permaculture course that the dazzling adult we admire is only the brief final chapter of a long life lived almost entirely out of sight, underwater.

A dragonfly spends the great majority of its existence as a larva, a nymph, submerged in the pond or stream, for anything from a few months to several years depending on the species. And the nymph is not some passive grub waiting to become beautiful. It is one of the most formidable predators in fresh water. Its signature weapon is a hinged, extendable lower jaw called the labium, folded beneath the head and fired outwards hydraulically in milliseconds to seize prey, a mechanism with no real parallel among familiar animals (British Dragonfly Society).

It can shoot out a fair fraction of the body's length in an eyeblink. With it, the nymph takes aquatic insects, worms, tadpoles, small fish, and quite readily other dragonfly nymphs, including its own kind. It even breathes and moves by an extraordinary trick, drawing water into a chamber in its abdomen to extract oxygen across internal gills, and expelling that water in a jet for a sudden burst of propulsion.

Then, one day, it climbs. The nymph hauls itself up an emergent stem into the air, its skin splits along the back, and the adult drags itself free, pumps fluid into crumpled wings until they harden into glassy panes, and takes flight. The whole beautiful, aerial, sun-loving adult phase that we think of as 'the dragonfly' often lasts only a few weeks. We have been admiring the coda and missing the symphony. Most of a dragonfly's life happened underwater, in the dark, as a hunter, before we ever saw it.

The near-perfect predator

The adult, brief as it is, may be the most efficient hunter on the planet. Controlled studies of dragonflies pursuing prey have recorded capture success rates of around ninety-five per cent, with individual studies ranging from roughly eighty-three to ninety-seven per cent (Combes et al., 2013). Set that against the figures usually quoted for celebrated predators, around a quarter for lions and roughly half for great white sharks, and the dragonfly is in a class of its own.

The secret is not raw speed but something closer to foresight. A dragonfly does not simply chase its prey. It intercepts, calculating where the target is going to be and flying to meet it there, the way a dog catches a frisbee not by running to where it is but to where it will be (Mischiati et al., 2015). Studies show the dragonfly holds its prey at a fixed point in its visual field throughout the pursuit, following the most efficient possible collision course and minimising wasteful corrections. This involves specialised nerve cells, target-selective descending neurons, that lock onto a single moving target and filter out the visual clutter of a whole swarm, feeding a kind of internal model straight through to the flight muscles. It is, in a tiny brain, something that looks unnervingly like prediction. All of this rides on hardware to match: eyes made of up to thirty thousand separate facets giving nearly all-round vision and a very fast visual refresh rate, and four wings that can be controlled independently, letting the animal hover, fly backwards, and turn on the spot, while its spiny legs fold into a basket to scoop prey from the air.

The greatest traveller of them all

If deep time and lethal skill were not enough, one dragonfly also holds a record that shames far larger animals. The globe skimmer, Pantala flavescens, a modest yellowish insect only about five centimetres long, undertakes the longest known migration of any insect on earth. Riding high-altitude seasonal winds, globe skimmers make a multi-generational circuit between India, East Africa, and central Asia estimated at somewhere between fourteen and eighteen thousand kilometres, which includes a non-stop crossing of the open Indian Ocean of several thousand kilometres (Hedlund et al., 2021; SaveOurSeas). Taking body size into account, it is considered the longest regular non-stop migratory flight in the animal kingdom, exceeding even the famous journey of the monarch butterfly. A creature lighter than a paperclip crosses an ocean. Britain has its own migrant dragonflies too, and increasingly so, which brings us to what dragonflies can tell us about the state of our own country.

A living verdict on your water

Because their larvae must have clean, well-oxygenated water to survive, dragonflies are among the finest natural indicators of freshwater health we have. The presence of breeding dragonflies at a pond is a genuine verdict: it means the water is alive and healthy enough to support a demanding top predator through years of larval life. Their absence is a verdict too. And read across a whole country, their fortunes become a live readout of a changing landscape.

The picture in Britain is a striking mixture of gain and loss. The State of Dragonflies in Britain and Ireland 2021, compiled by the British Dragonfly Society from more than 1.4 million records submitted by 17,000 people between 1970 and 2019, found that 41 per cent of species had significantly increased their range while 11 per cent had declined (Taylor et al., 2021; UKCEH, 2021). The winners are the warmth-loving species, because dragonflies are at heart tropical insects and a warming climate suits many of them: the emperor dragonfly has surged northwards, six new species have colonised Britain since the late 1990s, and the dainty damselfly returned in 2010 having been lost to a coastal flood back in 1953. The losers tell the opposite story. The specialists of cold upland bogs and pools, such as the black darter, the common hawker, and the emerald damselfly, have declined, squeezed by the draining and drying of the boggy habitats they depend on (UKCEH, 2021).

It would be easy, and wrong, to read the headline and conclude that climate change is simply good for dragonflies. It is, for now, a net gain for British species overall, but that is a fragile and temporary verdict. The same report warns that the benefits could soon tip into harm, as extreme floods and droughts kill juvenile dragonflies and rising seas inundate the coastal wetlands they breed in. And underneath the climate story sits a plainer, older loss: something like three in every four ponds were lost from England and Wales over the twentieth century, along with drained marshes and polluted rivers (State of Dragonflies, 2021). The dragonfly, in other words, is a barometer of both a warming climate and a drained, wetland-poor landscape, and it is reading both at once, in your garden.

The one wild wonder you can actually summon

Which brings us to the most hopeful thing about dragonflies, and the reason they deserve a place in any garden-scale conversation about nature. Most of the great rewilding stories are out of an ordinary person's hands. You cannot put a beaver in your garden or restore a river from your back step. But you can, with very little effort, add a three-hundred-million-year-old apex predator and a living water-quality gauge to your own patch, and you can do it fast.

The single act that does it is digging a pond. Even a small one, given a year or two, will attract dragonflies, and a well-made one will have them breeding. The recipe is simple. Give it some deeper water and gently sloping, shallow margins. Plant native marginal and emergent plants so that larvae have stems to climb when it is time to emerge, and some submerged oxygenating plants for the underwater world. Put it in a sunny, sheltered spot, because dragonflies love warmth. Keep it free of fish, which eat the larvae and will quietly cancel the whole enterprise. Never use pesticides anywhere near it. Then wait, and watch. Given that three in four ponds have been lost, every new garden pond is a small reversal of that century of draining, a stepping stone in a landscape that has had most of its stepping stones filled in, and every garden sits somewhere in a catchment.

So the next time a dragonfly hangs at the edge of your pond, look again, because you are not watching a pretty insect. You are watching the incredibly brief airborne finale of a long life spent hunting underwater, a design older than the dinosaurs, a cousin of the ocean-crossing record-holder of the insect world, one of the deadliest hunters ever measured, and a verdict that your water is clean and alive. And it came because you dug a hole in the ground and filled it with water. Few gestures so small have ever summoned anything so ancient.

References

Meganeura and the Carboniferous giant insects, and the antiquity of the Odonata lineage: standard palaeontological accounts, e.g. Natural History Museum, London, and the fossil record of the Protodonata / griffinflies (late Carboniferous, roughly 300 million years ago; wingspans approaching 70 cm, associated with elevated atmospheric oxygen).

British Dragonfly Society. Larval (nymph) biology, including the extendable labium and rectal-gill respiration and jet propulsion. Available at: british-dragonflies.org.uk.

Combes, S. A. et al. (2013). "Linking biomechanics and ecology through predator-prey interactions: flight performance of dragonflies and their prey." Journal of Experimental Biology / reviewed in Integrative and Comparative Biology. Source for capture-success rates of roughly 83 to 97 per cent, commonly around 95 per cent, in controlled study conditions.

Mischiati, M., Lin, H.-T., Herold, P., Imler, E., Olberg, R. and Leonardo, A. (2015). "Internal models direct dragonfly interception steering." Nature, 517, 333 to 338. Source for predictive interception, target-selective descending neurons, and the internal-model account of dragonfly hunting.

Hedlund, J. S., Lv, H., Lehmann, P., Hu, G., Anderson, R. C. and Chapman, J. W. (2021). "Unraveling the World's Longest Non-stop Migration: The Indian Ocean Crossing of the Globe Skimmer Dragonfly." Frontiers in Ecology and Evolution, 9. See also Anderson, R. C. (2009), Journal of Tropical Ecology, on the proposed India to East Africa crossing.

Save Our Seas Foundation. Wanderlust Dragonflies? (globe skimmer migration of around 14,000 to 18,000 km, including an Indian Ocean crossing of over 3,500 km). Available at: saveourseas.com.

Taylor, P., Smallshire, D., Parr, A. J., Brooks, S. J., Cham, S. A., Colver, E. F., Harvey, M., Hepper, D., Isaac, N. J. B., Logie, M. W., McFerran, D., McKenna, F., Nelson, B. and Roy, D. B. (2021). State of Dragonflies in Britain and Ireland 2021. British Dragonfly Society, Old Weston, Huntingdon.

UK Centre for Ecology and Hydrology (2021). UK's dragonflies are benefiting from climate change (analysis for the State of Dragonflies 2021: 41 per cent of species increased in range, 11 per cent declined; 1.4 million records from 17,000 recorders, 1970 to 2019; emperor dragonfly the largest range gainer; black darter, common hawker and emerald damselfly among the greatest decliners). Available at: ceh.ac.uk. The figure that around three in four ponds were lost from England and Wales during the twentieth century is drawn from the same report and from Freshwater Habitats Trust pond data.