Of all insects there are few that capture our attention and interest the way dragonflies do. They have, perhaps, the coolest, most evocative name of any group of insects: Dragonfly. In English there are a great number of other common categorical names: Devil’s Darning Needle, Snake Doctor, and Ear Cutter among others. Many of these names come from the mystifying apparent fear of nature that crops up over and over in European views of the world. Many European cultures viewed dragonflies as sinister creatures, servants of the devil, in league with other evils such as snakes and bats.
Other cultures, often more agrarian ones, had a far more benign view of dragonflies, based, perhaps, on the recognition of their fundamental role in controlling populations of pest insects of all sorts. An archaic name for the Japanese Islands is Akitsushima (秋津島), the Dragonfly Islands, where dragonflies symbolized courage, strength, and happiness. For some native American tribes dragonflies symbolized clean, pure water, swiftness, and agility. In the modern world dragonflies are good indicators of environmental heath, indicating a robustly functioning ecosystem.
Dragonflies and their close relatives, Damselflies, come in a dazzling array of colors and patterns, ranging in size from less than an inch long up to the South American Megaloprepus caerulatus with a wingspan of over 7 inches. The largest dragonfly we know of is from the 300 million year old fossil Meganeura that had a wingspan of over 2 feet.
Dragonflies are powerful hunters, both in their nymph and adult stages. Dragonfly nymphs are aquatic and prey on any animal or insect they can grab with their claws or their extendible jaws. Insects, small fish, tadpoles, and small amphibians are all food for these voracious predators. The nymphs are large, and, in turn, are prey for a wide range of other animals, insects, birds, and fish. Elva Paulson has some wonderful watercolors of a dragonfly emerging from its nymph stage. Humans are included as predators, many Asian cultures eating both dragonfly nymphs and adult dragonflies as delicacies. One of the most tasty things I’ve eaten (from a long list of foods most people would consider to be unusual) was a plate of deep fried dragonfly larvae. Absolutely delicious. In Beijing I would sometimes find adult dragonflies candied in liquid sugar, their wings crispy with the hardened sugar.
The adult phase of a dragonfly’s life is short, in temperate climates only the length of the summer. This is their mating stage and it takes them between 2 months and 6 years living under water to reach this stage. Dragonflies are extremely active during this mating phase and must eat often. They have enormous eyes giving nearly 360 vision, incredibly swift reactions, fast, powerful flight, and wicked barbs on their legs to assist capturing insects in flight. The inset above shows these barbs.
The common names of dragonflies often reflect their speed or their abilities as hunters. Meadow-hawk is one of my favorite names, and watching one dart away to catch an insect and return to its roost to devour it definitely brings hawks to mind.
Dragonflies are powerful fliers. They have been clocked at over 35 miles an hour, fast enough to get a speeding ticket in a school zone, and, like hummingbirds, can fly forwards, backwards, sideways, up and down, and hover. Their backs are sloped where their wings anchor, placing each pair at different heights, allowing for tremendous wing mobility. Some species of dragonfly migrate, but the scale of some of those migrations has only recently been realized. One dragonfly species in particular, the Globe Skimmer (Pantala flavescens) flies from India to Africa and back, island hopping cross the Indian Ocean, making open water crossings of nearly 1000km (620 miles) between island stops. The only places they can breed are at the Indian and African ends of the migration, many of the islands they use as stopover points do not have sufficient freshwater for dragonflies to breed. This is a stunning feat of flying for an insect and may be a behavior that evolved as a result of plate tectonics splitting India and Africa apart, eventually thrusting India into Asia. If so, this migration could have begun 135 millions years ago. Unfortunately, we have no reliable way of telling if this is the case.
Last year was a good year for dragonflies in Vermont, and this year looks like it is shaping up to be a good one as well. The ecologist in me cannot help wondering why and one idea is that it may be linked to the calamitous drop in bat populations as a result of white-nose disease, a fungus that infects hibernating bats, weakening and eventually killing them. It may be that adult dragonflies have more to eat with fewer bats and a greater percentage of them are surviving through the summer. There is a historical precedent for this sort of boom in insect populations. During the Great Leap Forward, Chairman Mao promoted a policy of killing off all things he thought were eating grain, birds amongst these. With the crash in bird populations in China the insect population exploded.
I am happy to see the dragonflies here. Their presence means that the water is clean, we will have fewer mosquitoes, midges, and black-flies, and they are extraordinarily beautiful creatures.
Three-hundred twenty-five millions years old and going strong. They have it figured out!