The White-letter hairstreak may be quite widespread in England and Wales but is, by no means, a common butterfly. Breeding on different varieties of elm, it fell into decline after the outbreak of Dutch Elm disease, prevalent in the 1980’s. It has experienced a recovery, in some areas, but is still listed as a priority species on the UK Biodiversity Action Plan.
There are a few local sites that support small colonies – the Ben Rhydding Gravel Pits being one, but it is worth keeping a lookout wherever there are elms. The Wych elm is our only truly native elm and is most common to our region. It is frequently found in woodland and hedges throughout our vice-county, including Wharfedale. It seems to have recovered well from Dutch Elm disease and some research has found White-letter hairstreaks to favour it over other varieties.
If you are out and about then keep an eye out. Wych elm’s leaves are characteristically rough on the upper surface and softly hairy beneath; the bark is smooth and grey. White-letter hairstreaks sometimes come down from the trees to nectar on flowers such as bramble, privet or, what is often the case at the Ben Rhydding Gravel Pits, creeping thistle.