Here be dragons!
I am really thrilled – after weeks of hoping and watching, I captured images of a nymph emerging as a dragonfly!
As I’ve written previously, there’s been a lot of activity lately amongst the big dragonfly nymphs in our pond. They are broad bodied chaser nymphs – Libellulla depressa - and they are ferocious looking critters. For the last two summers I’ve managed to get photos of large red damselflies emerging (they’re on my page HERE) but I was really hoping to see one of these fearsome nymphs emerge, as they’re at least ten times the size of the damselfly nymphs. A couple of weeks ago, when the sun came out for the first time in ages, I noticed the nymphs crowding at the surface of the pond. They seemed to be sunning themselves and acclimatising to breathing air. I blogged about it HERE. Since then, I’ve been up and down the garden to the pond over and over again, hoping to catch one emerging. No joy though, until Friday, when I started finding exuviae (the empty cases left when the dragonfly emerges) all over the garden. I was gutted, frankly, because whereas the damselflies crawl up the stems of emergent vegetation to do their thing, I realised that these big buggers were crawling up to six metres away from the pond before undergoing their final moult. Talk about finding a needle in a hay stack! Where we found exuviae, we also often found a shiny dragonfly wing – a sign that it had been predated before it was strong enough to fly. We have a gang of resident sparrows who work the garden as effectively as a gang of pickpockets work Oxford Street; there aren’t many insects that escape their beady eyes, especially not one as large and tempting as a defenceless dragonfly. All in all, my hopes of getting my dream pictures seemed to be fading fast.
Before we go any further, here is more than you’ve probably ever wanted to know about dragonflies.
First, The Short Version:
Dragon and damselflies are closely related insects which are recognisable by their bright colours and elongated bodies. These insects that you see flying around are right at the end of their life – most of it has been spent underwater looking nothing like they do now. If that’s all the info you want, then you could skip straight to the VIDEO and scroll to the bottom for the slideshow.
But the The Long Version is better!
Dragonflies and damselflies are insects of the order Odonata. The ‘true’ dragonflies are of the suborder Anisoptera, whereas damselflies are classified as Zygoptera.
They are quite easy to tell apart really; at rest, dragons perch with their wings spread out to each side like this keeled skimmer…
Whereas damsels perch with their wings folded along the length of their back, like this large red damselfly.
Also, as you can see from the pictures, dragons are much bigger and stronger than damsels. If you see a little delicate jewel of colour fluttering about over the river, it’s a damselfly. If you see a big streak of colour zoom past you at speed, it’s a dragon! What many people don’t realise, though, is that these beautiful aerial predators are the culmination of a life cycle spent mainly underwater. Both dragon and damselflies have a larval, or nymph stage which is completely aquatic, spending between several months and several years living underwater, before finally emerging into the air to transform into a flying insect. In all their incarnations, though, they are fearsome predators, whether it be of water fleas or midges, tadpoles or butterflies.
Dragons and damsels lay their eggs in or near water during the summer months. Some species (like hawkers) deposit their eggs out of the water on nearby logs or vegetation and the eggs don’t hatch until the following spring, whereupon the tiny larva has to wriggle its way to the water. Most species though, chasers included, lay their eggs in the water and the eggs hatch a few weeks later. Once hatched the nymph moults its skin many times as it grows. Each period between moults is known as an instar, and chaser nymphs can moult ten or so times during their aquatic phase, each instar larger and more developed than the last. You can see the wing buds developing in the later instars. Damselfly larvae have three caudal gills protruding from the end of the abdomen with which to extract oxygen from the water. Dragonfly larvae do things slightly differently; they breathe through their anus. The rectum of a dragon nymph is a specially adapted chamber for gaseous exchange – they draw water in through their anus, absorb oxygen into the tracheal tubes, and pump the water out again. Gives a whole new slant on the phrase ‘talking out of your arse’ – they actually breathe through it!
Broad bodied chasers are what’s known as a spring species. This means that the nymphs enter their final instar state and then pause for several months (known as diapause) – they no longer grow but enter a period of arrested development. This allows all the nymphs to sychronise their development in preparation for a mass emergence in the spring. So the eggs are laid in mid – late summer and hatch soon after. The nymphs progress steadily through the instar states for the first summer, autumn, winter and spring. During their second summer their growth rate slows, until in the autumn they moult for the penultimat time and enter diapause – this is thought to be triggered by the autumn equinox. They stay like this all of their second winter, eating and doing whatever dragonfly nymphs do for fun (hanging around waiting for something to swim by, mainly), but not growing or moulting or changing any more. Then, as the days lengthen and temperature increases during the spring, they prepare to emerge. As dragons and damsels don’t have a pupal stage, their developmental process is known as incomplete metamorphosis; they transform directly from instar to imago (adult).
Right, that’s the technical stuff out of the way. Now for the photographs!
On Saturday morning I woke up at 5.30am. Instead of putting my ipod on and going back to sleep like I usually do, I found myself tempted by the birdsong and sunlight reaching fingers through the curtains, and thought I’d have a look around the pond and see if I could spot any nymphs. After 20 minutes of searching that only showed me how very many slugs and snails live in our garden, I decided to go back to bed. Just as I walked away from the pond, I found this little girl crawling determinedly away from the pond.
Blimey I was excited! I was determined not to let her out of my site, both for her protection and because I so wanted to photograph the process. The trouble was though, she was heading very purposefully for the long grass, where I wouldn’t have a hope of keeping track of her. I redirected her several times, but she didn’t like my carefully selected suggested locations for metamorphosis.
As we’d found quite a few exuviae on the patio, and since I saw at least two nymphs get eaten by sparrows there whilst I was guarding mine, I decided to put her on the patio. Here’s her close-up.
After crossing the patio, she climbed the wall of the house. I was a bit concerned she’d go up out of reach but luckily she stopped at shoulder height behind the jasmine.
After quite a lot of shifting about, she took up position. There was a lot of stretching and wriggling, especially of her legs. She became completely still and after ten minutes or so her nymph skin split across the thorax, revealing the brightly coloured dragonfly within.
I love the fact that you can see how huge her dragonfly eyes are – they take up all of her face, yet she’s been looking out through those tiny little nymph eyeholes. It must be like wearing glasses that only allow you to see through an centimetre diameter hole in the middle of the lense, then taking them off and seeing properly for the first time.
She eases her head out of the larval case…
…and here is her new face!
You can still see the ‘pimples’ on the lateral borders of her eyes where they fitted into the nymph eye holes.
She pulls her thorax and legs free of the exuvia, doing a sort of dragonfly mexican wave in the process.
The white strands that you can see are tracheal tubes that were involved in nymph respiration.
She flips her body back, hanging downwards (this wall is vertical, but I’ve rotated the pictures to they’re easier to look at).
Amazing view of her belly as she hangs downward here…
And a close up of her jaws…
She finally has all of her legs out, and her wing buds are still tightly shrivelled. The tracheal tubes are clearly visible from nymph thorax to dragonfly thorax.
Her mouth parts harden and look more fully formed. She is incredibly vulnerable throughout this process.
Finally she extricates her abdomen from the exuvia and flips herself upwards so that she is straddling her old body.
The contrast with her previous form is clear to see. Dragonflies have compound eyes, with up to 30,000 facets. She can see far more colours than we can, including ultra-violet.
She begins to pump haemolymph (the dragonfly’s verson of blood) into her wings, filling and extending them. It’s almost like blowing up a balloon.
Her wings fill and lengthen, the creases evening out.
Still crinkly, but now they look like wings…
And then suddenly, she looks like a dragonfly!
Her wings become more transparent as they begin to harden, and her body lengthens.
Finally she is full sized. She remains utterly vulnerable to predation, as she has no defence and no means of escape yet.
Over four hours since she emerged from the water, and she is ready to open her wings into the characteristic spread position of the dragonfly…
Flexing her wings, she is almost ready for her maiden flight. Dragonflies can move each wing independently, giving them astonishing aerial maneuverability. They can fly backwards too.
She took flight at 10.20am. Four and a half hours from start to finish – from nymph to dragonfly. What an amazing transformation! She will only live for a matter of weeks. Once she has taken on the colours and form of the fully mature adult, she’ll be ready to breed. I hope she comes back to our pond and starts the cycle of life all over again.
This entry was posted on May 28, 2012 by theforagingphotographer. It was filed under Dragonflies, Macro, Pondlife, Spring and was tagged with anisoptera, broad bodied chaser dragonfly, dragonfly nymphs, emergence, exuvia, larva, Libellula depressa, macro, metamorphosis, nature, odonata, photographs, pond, scary face, tracheal tubes, transformation.