Thirty

Over the weekend I saw a post by a local photography friend about a damselfly he'd photographed at NT Croome a week previously, which looked to me like a Willow Emerald. Today he said that the record had been confirmed - the first for this species at this site - and I promptly abandoned a tentative plan to drive to Cambridgeshire in search of my nemesis, and decided to try Croome instead.

Heading straight to the carriage splash at one end of the artificial "river" where P had found his specimen, I was dismayed first by the weather, which closed in very quickly and forced me to take shelter under some large oaks, and then by the realisation that the carriage splash pool was much larger than I remembered, and scanning it effectively would require the binoculars that were locked in the boot of my car, about a mile away in the car park. All I could really do was stand and wait, and watch for anomalous movement amongst vegetation that was constantly swaying and shifting in the stiff breeze.

After around ten minutes the rain stopped, and I moved out onto a bridge that spans a weir on the west side of the pool. And then, about quarter of an hour later, the clouds parted and the sun emerged, bringing with it a flight of Common and Ruddy Darters and several Migrant Hawkers, who began patrolling, hunting, and fighting (and if they were lucky, finding partners and copulating) all around the pool. 

Still I stood and watched - and then, just in front of me, came a delicate fluttery movement, as a well-camouflaged damselfly moved along the top of the reeds. When it settled I groaned aloud, because I could barely see it through the intervening foliage, but I found it with the camera eventually, and immediately knew that I had my quarry: species 30 of my Odonata year, the Willow Emerald Damselfly. Over the next minute I tried to get into a position that improved my view, but all I was able to do was move a little to my right and crouch on the bridge, so as to shoot between the bars. My second photo shows more clearly than this one the spur mark on the side of the thorax, which coupled with the light brown wing spots is diagnostic of this species. It also shows that this is a female, which is interesting because P's specimen last week was a male - so potentially there is a breeding pair of Willow Emeralds at Croome.

The reason this matters is that this species is a new colonist of the UK. Prior to the Millennium there had only ever been two well-documented sightings in this country, but in 2009 the Willow Emerald began to be recorded in increasing numbers in East Anglia. At first it spread slowly, but in 2015 it was sighted in eight southern and eastern counties, and since then it has surged northwards and westwards. It reached Worcestershire last year, but was recorded at just one site; however, so far this year it's been seen at five, of which Croome is the most recent.

One characteristic of the Willow Emerald that makes it unusually tricky to find is that it prefers to spend its time in trees rather than on low vegetation. These are usually willows or alders that overhang still or slow-flowing water such as ponds or canals, where the males will defend small territories and search out females. After mating, a pair will stay in tandem while the female inserts her eggs into the bark of one of these two trees, where they will remain in diapause through the winter before hatching in the spring. The larvae drop into the water below and undergo very rapid growth, emerging as adults as little as three months later. The Willow Emerald season can begin as early as May, but new adults have quite a long maturation period away from water before coming back to breed. The peak season is from July to September, with some individuals surviving well into the autumn in a mild year. It's thought that Willow Emeralds peak this late in the year so as to lay the bulk of their eggs when it's starting to get colder, so there is less danger of them hatching early, and the larvae being exposed to winter water temperatures.

This is your weekly reminder that I will be running another Tiny Tuesday challenge tomorrow. Please do join in if you can, with a close-up photo of some very small thing. The tag that will help me find the entries is TT433. I'll choose my favourites and hand out stars and hearts on Thursday or Friday.