The Black Darter is Britain’s smallest dragonfly, at an overall length of around 3.5 cm. It’s a species of moors and heaths, where it breeds in acidic pools and the shallow water at the margins of lakes, and it flies from late summer into autumn.
This is a mature male, easily distinguished from any other Darter by his very dark colouring; the brown patches on his abdomen will have started yellow, and he will also have had yellow patches on the sides of his thorax, but these darken progressively with age. The dark colouration is thought to help with heat retention in cooler regions – and despite the bright sunshine today it was distinctly brisk up on top of the Long Mynd. Males aren’t especially territorial, though I did see some short chases today, probably because all the males at the pool were waiting for the arrival of unmated females.
Female Black Darters wear a rather smart yellow and black livery, and I was sorry not to see any today. But they tend to hang out away from the breeding pools during the early part of the day, where only the most observant males will find them; any that haven’t mated by the afternoon will come to a pool, where they will fly around very fast and wait to see who is quick enough to catch them. Oviposition sometimes happens in tandem, or the female may lay her eggs alone, with the male hovering nearby to see off any rivals. The most favoured sites for oviposition are places with sphagnum moss, into which the developing larvae can crawl if the water level at the pool drops during their development. Eggs laid this year will enter diapause over the winter, and the larvae will develop next spring, to emerge around July.
I was extremely lucky at Carding Mill Valley on Thursday, to be approached by a chap who asked what I was trying to photograph, and who then showed me some photos of Black Darters he’d taken a couple of hours earlier at this same spot. He gave me a precise grid reference from the EXIF data, and when I got home I was able to look this up, compare satellite images with his description of the site, and pinpoint it. This morning I drove straight there, and within ten minutes of arrival was kneeling in boggy ground, happily photographing these dashing little dragons.