The Willow Emerald Damselfly (Chalcolestes viridis), one of Britain’s newest natural colonist species, has been found and photographed by bicycling birder Ian Stewart at Ruxley Gravel pits on 6th September. The identification, and status as the first record of the species in the London Borough of Bromley have been confirmed by the London Natural History Society Odonata recorder Neil Anderson.
Ian said “On 6th September at Ruxley GPs I saw an emerald damselfly species in a tree, quite co-operative but I was unable to focus my phone camera properly for a pic. A little later I returned to the same spot and found at least another 5 including a pair mating and ovipositing in the trees and after many attempts I managed a decent shot of what I’m sure is a Willow Emerald.”
Having consulted my ID guides I was 98% sure he was right, but forwarded the information to Neil just to be sure, and because he would be interested in the record. Neil replied “Congrats on the first Willow Emerald for Bromley. The fine photo shows all the salient ID features- lack of pruinescence, pale pterostigma (though immatures of L. sponsa can be pale), whitish appendages + crucially the spur on the side of the thorax. It’s been a good year for them in the London area- mainly in the SW part, though also present at Rye Meads in the NE. I think this species will be pretty widespread in a few years, though is easy to overlook as it often sits up in trees/bushes.”
The species appeared in East Anglia around 2007, and is now well established in east Norfolk, Suffolk, Essex and north Kent. In August 2014, a thriving colony was found near Redhill in Surrey, sufficiently far from other known sites to suggest that the species was more widespread than previously thought.
I have been on the lookout for it in Bexley for the last couple of years, including looking at Crossness and Thames Road Wetland in winter for the scars on tree and shrub branches arising from its unusual habit of laying its eggs under the bark of woody plants overhanging water. So far no success, but there now seems a strong chance that if it is not in our Borough already it soon will be. Foots Cray Meadows must be the leading contender for the first Bexley record.
The Willow Emerald is one of several species of Odonata now colonising the UK from the continent. So far the Small Red-eyed Damselfly, now well-established at a number of Bexley sites, has been the most successful in terms of rapidity of spread and persistence.
For more information about the Willow Emerald see:
Chris Rose (author, Checklist and account of the Dragonflies and Damselflies of the Borough of Bexley)