It’s all about the wings
Freshly emerged (or ‘teneral’) Common Darter - D Pritchard
Let's be honest: if a dragonfly crawled through the grass running down other creatures to eat, most people would find them utterly terrifying.
There's something about the addition of wings that adds a layer of magic to them, and has us marvelling at their beauty and agility.
As with things in nature though, there's more to them than just good looks. They're quite miraculous.
One of the questions most regularly asked in this area is "what's the difference between damselflies and dragonflies?"
Damselflies are able to hold their wings together above their abdomens, while dragonflies cannot. But care must be taken with this: Emerald damsels are sometimes called Spreadwings for their habit of keeping their wings open, and newly emerged dragonflies can close their wings until the tissues harden.
The most definitive characteristic is that damselflies have four identical wings, while dragonflies have two pairs of different sizes. If you remember this, you won't go far wrong.
The wings don't get a chance to practice. A fully grown dragonfly nymph leaves the water with a complete set of wings folded into little backpacks about one fifth the length of the adult wing. The nymph basically takes off a wetsuit, stretches it, and flies off with a fully working set of wings.
Origami experts have spent years trying to understand the physics involved in this, and have used their discoveries to developed technology such as weather balloons and parachutes for the Mars Rover.
Emerald Damselfly showing four identical wings characteristic of damselflies - D Pritchard
Wings of an Azure Damselfly right after emergence - D Pritchard
If you see a dragonfly while the wings are drying out, then it's really important not to touch them, as you can cause permanent damage. But there is no better time to appreciate their design. They have a crystalline appearance, and you'll see that they are far from flat.
Once unfolded, the wings are supported by a network of veins. If you've ever seen an inflatable tent, you'll understand the principle. The shape and pattern of the veins is not random, and it is often possible to identify species, and in some cases sex, from the wings alone.
Common Darter wing profile - D Pritchard
Here are some other wing facts:
The wings are counterbalanced with a pterostigma at each tip. These may aid recognition between species, strengthen the downbeat of each flight stroke and improve flight efficiency
The wing surfaces are covered in "nanopillars", like a microscopic bed of nails which can shred cell walls. This makes them naturally antibacterial, and has been mimicked by scientists to make coatings for for handles in hospitals.
Each wing also has a flexible joint halfway along called the node, made of resilin, which acts like a shock absorber to prevent breakage as well as increasing manoeuvrability.
Dragonflies can independently move each wing, and flap them out of phase with each other. Studies have shown that this can improve aerodynamics by up to a quarter.
In species with metallic wings (like the Banded Demoiselle, seen along the River Dearne), the colour comes not from pigment (although this may also be present), but from the refraction of light caused by the molecular structure of the wing surface itself, in the same way as the naturally brown feathers of a kingfisher. It has been found that the entire surface can absorb oxygen, and that the content of oxygen within the wing may contribute to the appearance of vivid blues.
The next time you visit Old Moor, try comparing the wings of the dragonflies and damselflies you see, and see for yourself that they are as diverse as the insects themselves.
Absolutely fascinating! Thanks for sharing David.
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