I enjoyed a little local excitement at the start of this week upon realising my top Odo aim for the year of self-finding a Willow Emerald Damselfly in my home county of Oxfordshire. For me the most difficult part of the day motivationally in retirement is mid-afternoon, when a sense of restlessness and boredom invariably strikes no matter how well I might have filled the time up until then. Sunday (13th) had become a lovely sunny autumn day and I could not face sitting it out in the garden.

With the butterfly season largely fizzling out and no notable new bird sightings locally to go after I opted for taking pictures of dragonflies, then tried to think of a venue that would not be crowded with general public. And so I decided on the Otmoor basin bridleway between Noke and Oddington where Blue-eyed (or Southern Migrant) Hawker were first discovered earlier this year (see here). This location I reasoned might offer a better chance of finding something unusual, and the spur of the moment aspect might increase the chances of Willow Emerald.

Parking in the village of Noke I duly trod the bridleway out to the old River Ray weir near Oddington where all that BE / SMH interest had played out. Regular Migrant Hawker, Ruddy and Common Darter were all plentiful but nothing of greater interest. All the while I scanned the track-side vegetation as best I could in search of the slim, metallic profile I was seeking. Then almost back at the route’s entry point (SP552131), suddenly there it was (pictured below) right in front of me.

The above female Willow Emerald Damselfly (Lestes viridis) was behaving in exactly the same way as had been described to me by one of the colleagues who had recorded another one during August prior to my then arrival. After relocating slightly due to my presence she hung in characteristic fashion from a dried bramble stem to which she would return over and again after flying out and back at intervals. I Googled the species on my phone then checked off the diagnostics. This was indeed my afternoon’s quest, and the self-found things are always the most satisfying.

The enlargement below shows the diagnostic detail to look for in the thorax. This is the largest and longest-bodied of the Lestes Spreadwing group at 39m- 48mm. Colouration is a relatively bright metallic green on the upper-parts and brown below, and the large pterostigma (wing tags) are pale brown with a cream centre.

A unique trait of Willow Emerald is that females oviposit into thin branches that overhang water. There the eggs overwinter before larvae hatch and drop down in the spring. They emerge as adults from about mid-July, with a peak in August and September. Egg laying involves scratching a small groove in the twig or host plant, creating distinctive marks in the form of “scars”. The process makes it easy to plot the presence of this species in winter and forms the basis of survey work currently being co-ordinated by the British Dragonfly Society.

Willow Emerald Damselfly (or Western Willow Spreadwing) has enjoyed a rapid and dramatic national range expansion over recent years. Though common and widespread across western and central Europe the late summer and autumn flying species was inexplicably absent in the British Isles through the 20th century. Despite an abundance of suitable habitat it was recorded reliably just twice in 1979 and 1992. More recently another was recorded in south-east Suffolk during 2007, before things took off in 2009 with a marked and sudden boom of 400 records from that area and north-east Essex.

From that time the damselfly has gained footholds in new south-east English counties north to Lincolnshire on a yearly basis. It is said to benefit from urbanisation, favouring garden ponds and park water features. But almost any kind of standing or slow-moving water with adjacent trees and shrubs may be favoured. I myself had observed WED just once before, at Maldon in Essex in September 2014, and I recall other Oxon wildlife colleagues going further into East Anglia to add it to their own lists.

The first record for Oxfordshire occurred in Wytham Wood to the immediate west of Oxford in summer 2019, and Willow Emerald was widely tipped to colonise the county further in the present season. The second record and first picture, a male came from Orchard Lake, Radley (SU519970) on 11th August. Another male was reported on that date at RSPB Otmoor, soon to be followed by a female along the Roman Road bridleway of Brown Hairstreak butterfly repute. Then from 7th September several records of both genders have issued from the Trap Grounds, adjacent to Port Meadow beside the north Oxford canal.

I myself had followed up on both those Radley and Roman Road sightings that are pictured above, but without connecting with either individual. With sunny weather forecast to persist through the week ahead I next elected to seek out more Willow Emerald locally, starting with the north Oxford site from where pictures had been published almost daily over the preceding seven days.

The Trap Grounds local wildlife area immediately south of the Frenchay Road canal bridge (OX2 6TF) comprises three acres of reed bed and seven acres of woodland, grassland, stream and ponds. The open access site is owned by Oxford City Council and managed for conservation, recreation, and education by a local volunteer group (see here). On Monday morning (14th) I found the cited main observation area in shade and it was plain that WED would most likely be viewable later in the day when it would only be possible to capture them pictorially into the sun, which was true of most of the published images from here. So I left this wonderfully well managed piece of habitat to its patch workers and volunteers and attempted further sightings of my own elsewhere.

Male Willow Emerald Damselflies at the Trap Grounds, Oxford

Over the next two and a half days I surveyed some other sites to the south of Oxford that I thought might be suitable, but without recording any more of the newest addition to Oxon’s Odo-fauna. Then on Thursday (17th) I returned to the Trap Grounds at what Adam had confirmed was the optimum time from midday into early afternoon. And with the benefit of guidance from and the practiced eye of patch worker Nicola, and also in company with Adam himself, I belatedly gained my own into the light studies of the resident males (pictured above). I now suspect that my insect agenda for 2020 may be closed.

For recent dragonfly and damselfly sightings in Oxfordshire visit our county recorder’s excellent Oxon Dragonflies website.