DORSET is braced for an influx of butterflies according to experts.

Millions of Painted Ladies could be winging their way to the UK from southern Europe as part of the longest butterfly migration in the world.

Unusually high numbers of the orange and black butterflies have been reported amassing in southern Europe at the critical time of the year for them to spread northwards into Britain.

The butterfly is a common immigrant that migrates in varying numbers from the continent to the UK each summer, where its caterpillars feed on thistles.

But around once every 10 years the UK experiences a Painted Lady ‘summer’ when millions of the butterflies arrive en masse.

Dorset is said to be a key area and anecdotal evidence suggests large numbers of Painted Ladies have already been seen along the coast over the last fortnight.

The last mass immigration took place in 2009 when around 11 million Painted Ladies descended across the UK.

Since then the UK has experienced five years with below average numbers but scientists are hopeful that 2015 could be very different.

Experts at Dorset-based Butterfly Conservation reported that some butterflies arrived during mid-May, but a spell of poor weather temporarily halted the immigration.

Recent warm sunny conditions have seen Painted Lady numbers soar once again.

The charity is asking for the public to record sightings of the butterfly to help chart the progress of any potential immigration during the summer.

Richard Fox, Butterfly Conservation Head of Recording said: “The Painted Lady migration is one of the real wonders of the natural world.

“Travelling up to 1km in the sky and at speeds of up to 30 miles-per-hour these small fragile-seeming creatures migrate hundreds of miles to reach our shores each year, even though none of the individual butterflies has ever made the trip before.”

The Painted Lady undertakes a phenomenal 9,000 mile round trip from tropical Africa to the Arctic Circle each year – almost double the length of the famous migrations of the Monarch butterfly in North America.

Research using citizen science sightings from the 2009 migration revealed that the whole journey is not undertaken by individual butterflies but in a series of steps by up to six successive generations.

Painted Lady sightings can be recorded via Butterfly Conservation’s Migrant Watch scheme.