Voting for the coveted Dragon of the Day award resolved down to a nail-biting head-to-head between this teneral female Emperor, and a male Four-spotted Chaser whom I photographed mid-emergence. In the end the Emperor (Empress?) won because I’ve never seen one at this early stage of development before – I generally don’t see them until they’re mature and ovipositing.
That I saw this one at all is thanks to the other two people who were watching the Mallard Lake reed bed at Lower Moor this morning: after chatting to them for a while, I went off for a quick jaunt along the track we Odonutters call Dragonfly Alley, and when I got back they’d found her and pointed her out to me. At that stage she was sitting quite low in the reeds, behind the marginal vegetation, and wasn’t easy to photograph, but quite soon she walked up this leaf to sun herself before making her maiden flight, and became fully visible. You may be able to see that her right forewing is slightly damaged – it must have come to rest against something as she was pumping it out, which folded it at this crucial stage and stopped it fully straightening. It won’t ever recover from this, and will probably make her slower and less manoeuvrable in flight than other Emperors, but a few minutes after I took this photo she did take a successful if fluttery maiden flight, over to the far side of the reeds, where she stayed for the next couple of hours.
According to Philip Corbet, contributing to the Bloomsbury Field Guide to the Dragonflies and Damselflies of Great Britain and Ireland by Brooks and Cham, Emperors can complete their life cycles in either one or two years, depending on the temperature of the water in which the larvae develop. Two years is more common, and in these populations emergence is coordinated: the final-stage larvae gather in shallow water around emergent vegetation, and after a couple of days of preparation (during which they begin to breathe air), one night they climb their chosen supports and transform. If it’s a warm night the entire business, including the maiden flight away from the water, is done and dusted under the cover of darkness, leaving just the evidence of their exuvia to show what has happened. But on a cold night (which it was on Tuesday) the emergence is split, with half the emergers coming out overnight, and half during the early morning.
This female is obviously part of the later group, and it’s tantalising to think that there will have been other Emperors in this reed bed this morning, in a similar teneral state. More tantalising, though, are the questions I still want to have answered: what process among the larvae decrees that tonight is the night for becoming airborne, rather than yesterday or tomorrow? And if it’s a cold night, who decides which larvae are to be in the first wave, and which in the second? Do the males go first, and the females second? Or does it just come down to size and aggression? I haven’t been able to find out the answers, and I really want to know!
There’s more about dragonfly emergence here. And I’ve posted the emerging Four-spotted Chaser to Facebook, if you’d like to see him.
