Tuesday 5 September 2017

Here be dragons!

This year I'm taking a special interest on dragonflies. They are a relatively small group, species are easy to identify in the field and they offer a range behaviours relatively easy to watch. In July I atended an FSC course on identification of aquatic macroinvertebrates and I immediately wanted to learn to identify dragonfly and damselfly larvae. A few days after the course I visited my local wildlife garden and went to the pond to check invertebrates. Something on the leaves of an aquatic plant called my attention. It was a dragonfly exuvia, the moulted skin of a nymph as the adult dragonfly emerges! 
My first dragonfly exuviae.
Dragonflies have incomplete metamorphosis, which means they lack a pupal stage. The dragonfly eggs hatch into nymphs which grow though several stages as aquatic predators. Nymphs lack functional wings or reproductive organs. The final nymphal stage will creep out of water and moult into an adult. There wasn't just a single exuvia though, there appeared to have been a mass emergence of Common Darter dragonflies and I counted over 50 of them. 
Several visible exuviae on iris leaves (13/07/17).
These are all the the exuviae I could reach from one end of the pond.
A close up of one of the exuvia looking quite intact. The adult emerges though the thorax.
The following week I had the chance to pop in the wildlife garden one morning. I checked the leaves for more exuviae and I was surprised to find two emerging dragonflies!
A Common Darter just emerging, head down, showing how the old nymph skin holds it to the leaf. On the top shot, one already drying its wings, folded back and still lacking pigmentation (both photos on 21/07/17).
This fresh adult male Common Darter, perhaps from the first emerging batch, was sunbathing by the pond.

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