Climate change is causing a striking butterfly from southern Europe to appear in record-breaking numbers in areas including Dorset, a charity reveals.

Lulworth-based Butterfly Conservation says more than 50 Long-tailed Blue butterflies and hundreds of the butterfly’s eggs have been discovered over the last few weeks, which could result in the largest ever emergence of the species in UK history.

Experts believe rising temperatures are behind the influx, with sightings of the exotic migrant coming in across the south of England.

Typically, only a handful reach the UK each summer from the Mediterranean, but this is the third time in six years that the butterfly has arrived in vastly increased numbers.

Butterfly Conservation volunteer and Long-tailed Blue expert, Neil Hulme, said: “These butterflies have crossed the Channel and are laying eggs in gardens, allotments and anywhere you can find Broad-leaved Everlasting-pea and similar plants, which the caterpillar likes to feed on.

“We’ve never recorded this many migrant adults before – it’s completely unprecedented. In only a few days, I’ve found more than 100 eggs in Sussex alone and the butterfly has been seen in Cornwall, Somerset, Devon, Dorset, Hampshire, Kent and Suffolk.

“What’s really exciting is that the Long-tailed Blue has gone further inland than it did in 2013 and 2015, with at least three confirmed sightings in Surrey, where the butterfly hasn’t been seen for 30 years.

“The adults will keep laying eggs and in September and October we’ll see the first British-born offspring emerging. I strongly believe this will take the total number seen this year to well over a hundred, breaking all previous records for this butterfly in the UK.”

The Long-tailed Blue has previously been considered a very rare visitor to the UK, despite being abundant across southern Europe, Africa, Asia and Australia.

The butterfly was seen for the very first time in Britain in 1859, but over the next 80 years only 30 adults were recorded. Significant influxes occurred in 1945, 1990 and most recently in 2015, but none of these equalled the invasion of 2013, when 109 sightings were recorded between July and October.

Neil Hulme added: “This is one of the world’s more successful species of butterfly. It may be small, but it’s a very powerful flyer, capable of crossing mountain ranges and seas."

Dr Dan Hoare from Butterfly Conservation said: “With unprecedented numbers of Long-tailed Blues and UK sightings of other rarities, like the Bedstraw Hawk-moth and Queen of Spain Fritillary butterfly, 2019 is certainly turning out to be an exciting year for immigrant species."

You can report Long-tailed Blue sightings to info@butterfly-conservation.org or through the free iRecord Butterflies app.