Britain has a new species of butterfly: the southern small white has continued its rapid colonisation of northern Europe by flying across the North Sea.
The species looks very similar to the native small, large and green-veined whites but two individuals spotted in County Durham and Suffolk this summer have been verified as Pieris mannii, which was once confined to southern Europe.
Assisted by global heating, the southern small white has made rapid progress across Europe since it was first spotted north of the Alps in France and Germany in 2008. It reached the Netherlands in 2015 and was recorded near Calais four years later.
“This is really exciting,” said Dr Dan Hoare, the director of nature recovery at Butterfly Conservation. “It’s always interesting when a new species turns up in the UK, but the southern small white has been gradually moving northwards through Europe for over a decade and we were just waiting for it to be seen in England for the first time. Top marks to the eagle-eyed snappers who not only got photos, but also realised the significance of what they’d seen.”
The southern small white is distinguished from the native whites by tiny differences in the black markings on its forewing tips. On a southern small white these are square in shape, with the black reaching down the outside of the wing to a point level with a black spot further in from the border. Free apps such as ObsIdentify, created by a Dutch non-profit foundation, are making identification easier – if people can obtain photos.
The first sighting was made by the birdwatcher Martyn Sidwell in Hartlepool on 1 July, and a second by William Brame at Landguard nature reserve in Suffolk on 2 August. The latter sighting was verified by Chris van Swaay, the chair of Butterfly Conservation Europe, who has been tracking the species’ progress for years.
Lepidopterists hope the species will now become established in Britain, assisted by gardeners. Unlike the large white, which is infamous for its caterpillars devouring brassicas, the caterpillars of the southern small white feed on candytuft, an evergreen shrub which is widely planted in gardens.
The sightings follow the sunniest ever spring on record, and a large influx of small whites migrating over the sea to Britain.
In the charity’s Big Butterfly Count this year, reports of the spectacular Jersey Tiger moth – a species which just a decade ago was restricted to the Channel Islands and the south coast of England – have risen 78% on last year, with sightings as far north as Birmingham.
Hoare added: “We always love to see butterflies and moths doing well in the UK, but we also know there are going to be winners and losers from the very rapid climate change we’re experiencing.
“One way we can increase the number of climate winners is by managing habitats positively so that threatened species can benefit as well as widespread mobile species. That means creating and maintaining good quality, connected habitat at a landscape scale.”
