Hunting the White-letter Hairstreak

A new Citizen Science project to try to locate this endangered butterfly in Ceredigion. We need your help!


Please do take a look at your Elms to see if you can see any  adults on the wing.  Now’s the time to check.  A pair of binoculars would be handy to see to the very top of the tree, and a camera to take a photo of the elusive beast!

The very latest update is that records have been made from Llanrhystud, Llechryd, Llanfarian, Cardigan and Clarach!  This is superb news and shows that there are more White-letter Hairstreaks in Ceredigion than we ever thought!  Please do keep hunting as they are only likely to be around for another 2-3 weeks on the wing.


We are delighted that Paul Taylor, our Vice County Recorder for Butterflies, saw 7 adults flying in the tops of Elms and feeding on bramble on the 4th of July 2023.  These were along the Rhydyfelin to Penparcau cycle path.  Please keep looking!

White-letter Hairstreak Caterpillars were found in Parc Natur Penglais, Aberystwyth, at Nanteos on the outskirts of Aberystwyth, and in Penparcau earlier in the year.    

Map of White-letter Hairstreak records

Latest White-letter Hairstreak records on 17th July 2023, thanks Paul Taylor for sharing his map.


Introduction – the background to this project

Our MP Ben Lake called it “a wonderful discovery” and it certainly was unexpected!  One sunny afternoon in July 2022 I was walking home through Penparcau, a small village in Ceredigion, past some Elm trees at the entrance to Bodlondeb Care Home, only to be startled by a small butterfly with obvious tails flying straight past my head!  I thought we might have an unusual immigrant species brought in on the hot winds of summer, but following it to an Elm leaf I discovered it was in fact the endangered White-letter Hairstreak Butterfly.  This butterfly had never been reported in the village before, so it was a huge thrill to see it.

Elm is the only food this butterfly’s caterpillars can eat, so if the trees were ever removed or damaged, this rare butterfly would die out.  The Elms in Penparcau, at Bodlondeb, and the ones close to it at the edge of Llwyn yr Eos School grounds, are now vital to this butterfly’s survival, because these Hairstreaks survive on a single small clump of trees or even one individual tree.  They will not move from one area to another, and will return to the same trees year after year.  Removing even one of these Elms might mean effectively wiping out this endangered butterfly from our village.  With this in mind I contacted the County Council and Ben Lake, letting them know that:

“This is wonderful news, but it does mean that we now have a responsibility to ensure these trees are protected from any future development.  This butterfly is one of the protected Section 7 Species: Environment (Wales) Act 2016 Section 7 – a list of the living organisms of principal importance for the purpose of maintaining and enhancing biodiversity in relation to Wales.”

I was pleased to have quick and promising responses from various members of Ceredigion County Council, giving me assurances that “we will recognise that we need to protect the butterfly and the trees.”  I join Ben Lake in thanking “everyone who has already undertaken action to ensure the necessary measures and protections are in place to safeguard the butterflies” and look forward to seeing these Endangered butterflies floating around Penparcau again next year.

What we want to do in 2023

Our aim is to get people to hunt for Elm in their part of Ceredigion, and once they have found some, using the resources listed below, to keep a special eye on it for the White-letter Hairstreak, and then, most importantly of all, to let us know!  We suggest looking for the adult from the middle of June to the middle of August.

If you would like help with identifying the butterfly, please see the resources below, and please send your White-letter Hairstreak sightings to Paul Taylor on the email below.


Thank you everyone!

Chloe Griffiths MA. BA. Cert. HE Field Ecology

Penparcau Wildlife Group