Dragonflies: The Ultimate Armoured Hunters of Ancient Design
I imagine that, like me, you are finding it necessary to drive very slowly around our beautiful island during these warm summer days and evenings. Along with our usual road companions, cyclists, hikers and baby deer, there are several other smaller folk occupying the driving corridors. I often stop to nudge a dozing garter snake off the toasty and treacherous tarmac, and have been making a concerted effort to avoid smacking into those dipping and diving wizards, the dragonflies. And yet it seems these collisions rarely occur, so I thought I’d investigate these flying marvels.
Insect Acrobats
Part of the answer lies with their compound eyes and 360 degree vision, plus a reaction time that is much faster than ours. In just 30 milliseconds a dragonfly can spot a moving object, decide whether or not it’s a potential meal, and catch it – all over and done before we slow humans could even begin to respond (see the BBC Earth video: “How do dragonflies see the world?”). As a comparison, our eyes capture up to 60 images per second from which our brain creates the illusion of a continuous image, but dragonflies see around 200 images per second and therefore spy much faster moving objects. In other words, they see the world in slow motion. As dragonflies can’t hear and have a limited sense of smell, this extraordinary sense of vision is essential to their survival.
Along with having excellent vision, dragonflies are true aerial acrobats and the world’s fastest flying insect. They have four wings which, unlike many other insects, they control with four separate sets of muscles. This means they have outstanding flight performance and efficiency, and are able to manoeuvre in six directions up, down, back, forward and sideways. It also makes them the most successful hunter in the animal kingdom with a capture rate of around 97% and flying speeds of up to 50 km/hour. And they achieve these feats of excellence with instructions from a brain the size of a pin head!
Damsel or Dragon?
Dragonflies and damselflies belong to a group known as Odonata which means “toothed jaws.” There are roughly the same number of dragonfly species in the world as there are mammals, and most live in the tropics. They can be sorted into two subcategories, “perchers” which, as the name suggests, hang out at local ponds perched on reeds, and “hawkers” who are much more active and spend most of the day in flight. Dragonflies spread their wings outwards when perched whereas damsels fold theirs neatly alongside their dainty torsos.
While the names Dragons and Damsels are reminiscent of medieval times, their life history is far more ancient than that. In fact, dragonflies witnessed the rise and fall of the dinosaurs, and have been on Earth for about 330 million years. Fossils exist of an early form of this insect that was the size of a crow. Now the largest measures about 16 cm, so they have evolved to become much smaller.
Dragons are the chunkier of the two, often seen hunting over fields, roads, fresh water, and at local island beaches where they help keep pesky mosquitoes under control. Damsels stay closer to their fresh water habitats and venture out in little sorties before heading back to their favourite perch to bask in the sun. Dragons generate body heat with their active movements, where damsels prefer soaking up the sun’s rays, but because of their delicate wings, both are strongly affected by bad weather and must seek shelter during heavy rain and winds.
Water to Air: Armoured Transformer
While we are much more aware of these creatures during their short summer lives, in fact they have two distinct life stages and go through one of the most remarkable metamorphoses in the natural world, from silent predators of freshwater realms to masters of the air. Under the tranquil surface of our local ponds lies a battlefield – Odonates in their bucolically-named “nymph” stage who lurk in the murk, preying on anything they can, including tadpoles, tiny fish and…each other! With huge eyes and stereo-vision, they stalk their prey like a cat, and have long jaws that measure half their body length which they shoot out to spear their victims. Video recordings of this behaviour would not make good bedtime viewing as these nymphs could easily serve as models for horror movie monsters.
After two to three years in the obscurity of the pond, where they moult up to fifteen times, these creatures climb up reeds during spring and change into the colourful flyers we are more familiar with. The nymph inflates its body to crack open its casing and, starting with its head, slowly emerges segment by segment from its old skin, transforming from an aquatic crawler to a flyer in just twelve hours. After a much briefer second stage of life, dragonflies return to their ponds to mate and lay eggs. If you visit the Japanese Garden at the end of the summer, you will likely see pairs joined together in a heart shape, which may look like a romantic gesture, but is actually a necessary contortion for the transfer of sperm to the female.
Local Species
Freshwater habitats are essential for dragonflies, and there are not many of these on Mayne Island. If you have space on your property to install a natural pond, why not try to create a place for these fascinating animals? Local naturalist Michael Dunn has a pond on his property, and he has identified 10 Odonata species on Mayne Island. Here is the current list:
Dragons:
- Shadow Darner
- Blue-eyed Darner
- Green Darner
- Canada Darner
- Cardinal Meadowhawk
- Striped Meadowhawk
- Eight-spotted Skimmer
- Common Whitetail
Damsels:
- Common Spreadwing
- Bluets sp.
A fun late-summer activity with the kids: dragonfly-spotting! They are easy to see, large and fairly easy to identify, don’t sting, and display a gorgeous variety of jewel-box colours: iridescent greens, sparkling turquoise, and deep crimson.
More Information
For further information on dragonflies and damselflies, a good reference book is:
Introducing the dragonflies of British Columbia and the Yukon by Robert A. Cannings, Royal BC Museum Press, 2002
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