Butterfly enthusiasts in the United Kingdom are gearing up for possibly one of the largest migrations of Painted lady butterflies (Vanessa cardui) to ever be observed in the country.

Millions of these orange and black creatures are expected to make their way to the British Isles from southern Europe this summer as part of their annual migration.

Painted lady butterflies are known to travel to the United Kingdom to allow their caterpillars to feed on local plants such as thistles. Once every 10 years, however, many of these arthropods arrive in the country en masse in a phenomenon called Painted Lady summer.

Experts believe the county of Dorset place an important role in this large migration of Painted ladies. Anecdotal evidence posits that a massive number of the butterflies have already arrived in areas along the county's coast in previous nights.

The latest Painted Lady summer occurred back in 2009. An estimated 11 million butterflies descended on the United Kingdom during the season.

Since then, locals and butterfly hobbyists only saw a few Painted Ladies visit the country in the past five years, but butterfly experts are optimistic that another mass immigration could occur this year.

Members of the Butterfly Conservation in Dorset reported that several butterflies came by the country in the middle of May, but poor weather in the country prevented the rest of the Painted Ladies to make the journey.

The improvement in the weather recently has allowed the butterflies to continue their migration this season.

The Butterfly Conservation has urged locals to document butterfly sightings to help its members monitor the migration of the Painted Ladies.

"The Painted Lady migration is one of the real wonders of the natural world," Richard Fox, head of recording for the Dorset Butterfly Conservation, said.

"Travelling up to one kilometer 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."

During their migration, Painted Lady butterflies often travel for about 9,000 miles from their habitats in tropical North Africa to the Arctic every year. The total area their journey covers is almost twice as much as the distance of the migrations of Monarch butterflies in North America.

Analysis of data collected from citizen science sightings of the Painted Lady migration in 2009 shows the entirety of the voyage is not done by individual butterflies, but rather by successive generations of Painted Ladies in a series of journeys.

Photo: Michael MK Khor | Flickr

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