Whatever happened to the Common Emerald Damselfly?
Back in the 1970s, a few hardy souls carried out a survey of the dragonflies of Sussex on behalf of the Sussex Trust for Nature Conservation (now the SWT). In 1979 we tried to get it published but no one was interested in Dragonflies back then so it stayed in draft form with a few copies in libraries etc. where it gathered dust until much of the data was incorporated into the excellent “Dragonflies of Sussex” which was published in 2004. I still have the old records of my original survey and, prompted by emails from Dave Smallshire of the BDS, I dusted off the card index and looked out those of the Common Emerald Damselfly (Lestes sponsa).
In the 1970s the Common Emerald was a locally common damselfly in the county. In some areas abundant, indeed, I have records from one observer (Bill Merritt) who observed “clouds of adults” at a number of sites. Advancing years means I do less field work in Sussex, but I have been hunting down Lestids (I admit to being a Lestid freak!!). In 2019 and 2020, I managed to find only a few breeding pairs at one site. My gut feeling is that this species is on the decline so you can imagine how my interest was sparked when I received the email from the BDS and I quote “…Emerald Damselfly has in recent years lost roughly 25–30% of its range in both Britain and Ireland, and the Netherlands, while in Germany the loss has been around 35%.”
It appears that a once common, and often overlooked, damselfly is declining and we need your help in finding out:
- Where it breeds
- Are there areas where “clouds of adults” can still be found?
Where to look – and when?
Although widespread back in the 1970s the Common Emerald was rather local; its strongholds were:
- The Rother valley in East Sussex and particularly the lowland levels
- Pevensey Levels. My old records state that it was common in all areas here
- Ashdown Forest
- Buchan Park and Tilgate near Crawley
- Amberley Wild Brooks
- The West Sussex Commons, Iping and Stedham and around Burton Pond
Is Common Emerald still at these localities and, if so, in what numbers. Of course there were other sites so keep a good eye out wherever you are looking.
Fig 1 is a picture of the only site in Sussex where I have found Common Emerald in the last two years! Emerald damsels are not good with predators; their strategy is to avoid them. They live short larval lives often in seasonal ponds (that dry out in summer). the Common Emerald does breed in permanent pools and ditches but in acid habitats where there are no fish (look at the very dark water here). All species have a liking for thin leaved vegetation such as rushes and sedges which border the pond, the adults display, mate and oviposit here.
Typical Emerald Pond
If you see the pond or ditch drying out, don’t panic; emeralds will stay even if the pond is dry. You will spot them resting with their wings open. Emergence usually starts around the middle of June and they can be found flying until the end of October; there are even old records from early November. The pairs usually lay in tandem into plant stems preferring rushes or sedges. If the pond has water, Common Emeralds can be seen moving down the stem and the female ovipositing below the water surface with the somewhat confused male following . Unlike other emeralds, Common Emerald often delays emergence and larvae can be found until mid August. If you look carefully you can see larvae close to the surface (Fig 2). Finally don’t forget to look for exuviae. They are quite large, with long legs and black or heavily patterned lamellae. They usually emerge about 10 cm above the water often on dead stems.
A Scarce Emerald larva resting near the surface of the water almost ready to emerge
What am I looking for?
Most damsels are hard to study, they are small and constantly on the move, Emeralds are much easier, they are quite large and conspicuous spending much of their mature life resting, displaying with their wings open waiting for the opposite sex to appear.
The Common Emerald is our main interest but there are four (possibly five) species that could be confused so here are a few tips on how to identify our Emeralds. Let’s not complicate matters, look for adult male insects not teneral and the following should be a useful guide. Females are more difficult. If in doubt send me a pic.
The rarest species in UK and the easiest to identify. There are at least three Sussex records but it has never been found breeding.
Pt is the pterostigma which is bicoloured (half brown half white)
It is a large damsel usually green like this one but sometimes brown. Eyes are brown (never blue)
There is no blue on this damsel except sometimes on abdominal segment 10 in males nowhere else
Now spreading through the UK but curiously rare in Sussex. Lays its eggs in branches of willow and other shrubs overhanging water
The pterostigma is light brown which is diagnostic.
It is a large green damsel with no blue markings except sometimes on the face. Eyes brown but can turn bluish with age
The subject of our survey
The Common and Scarce Emeralds both have extensive blue pruinescence. Pterostigma is almost black with thin white lines at each end
Abdominal segment 2 is usually completely blue
Eyes dark dull blue
The above are not always reliable.If in doubt you need to look at the apps (appendages) which are quite straight in the Common Emerald and club shaped in the Scarce.
Not recorded in Sussex, apart from isolated records, since the 1950s but there are colonies on seasonal ponds in Kent.
Very similar to Common Emerald except:
Abdominal segment 2 is usually half blue half green as shown here but the top half can also be completely green.
Eyes bright blue.
On this specimen you can say the apps (appendages) which are club shaped.
And finally another possible species…
Small Emerald (Lestes virens vestalis)
Similar in size to Common and Scarce Emerald and easily confused with both. This species has never been recorded in UK but is only just over the Channel and could easily be overlooked.
- Pterostigma is almost black with thin white lines at each end.
- Abdominal segment 2 without any blue colouration above or below
- Abdominal segments 9 & 10 only blue (Common and Scarce have blue on segment 8 as well)
- Eyes blue like Common Emerald.
- For final confirmation you need to look at the apps (appendages) which you can see here are very short.
Find this beast and you can expect champagne or roses whichever you prefer…
What do I do with my records?
I am happy to receive your records, just send your information to firstname.lastname@example.org Remember negative records are important so if you spend the summer without success we need to know.
And finally – good hunting in your Emerald summer!
State of Dragonflies in Britain and Ireland 2021
The British Dragonfly Socoiety’s 'State of Dragonflies in Britain and Ireland 2021' report is now out and can be accessed at
https://british-dragonflies.org.uk/recording/state-of-dragonflies-2021/. It outlines increases and decreases of species across Britain and Ireland over the past 50 years and is based on data from 17,000 observers.