A butterfly that was once extinct in the United Kingdom has experienced its best summer in 150 years.

The huge blue butterfly is one of the most endangered butterflies in Europe, but thousands have been spotted in southwest England this summer.

It is the result of a Royal Entomological Society-led long-term conservation endeavor.

According to scientists, the success story demonstrates how endangered animals can be saved.

The conservation efforts at roughly 40 sites in Somerset and the Cotswolds also benefited a great number of other rare species.

In 1979, the huge blue was declared extinct in the UK. Four years later, caterpillars from Sweden were sent to England in an attempt to reestablish the species.

One of the two individuals that restored the butterfly in 1983, research ecologist David Simcox, stated that it was “very gratifying” to observe their current success.

“I did not have a single grey hair when I began. Now everything is grey “He stated.

Mr. Simcox and his colleague, Oxford University professor Jeremy Thomas, did not anticipate this level of success in the 1980s.

Mr. Simcox remarked, “Obviously you have hope, but the first ten years were challenging; the national population was less than 10,000 eggs.”

In contrast, conservationists tallied 750,000 huge blue butterfly eggs this summer.

They estimated that over 20,000 butterflies were flying, making the southwest of England the largest known butterfly colony in Europe.

The effort focused on rehabilitating a sort of wild meadowland in which the huge blue prefers to reside.

Prof. Thomas remarked, “This is one of the oddest butterflies in the world.

It spends most of the year as a caterpillar within the nests of red ants, where it feeds on grubs. This lifecycle makes protection more difficult.

Mr. Simcox emphasized that reversing the trend of extinction is possible if we can comprehend the ecological requirements of extremely uncommon and challenging species.

He cautioned that although the giant blue butterflies are currently thriving, they remain vulnerable and their long-term survival is uncertain.

Two unfavorable years or inadequate land management might be disastrous for the species.

Extreme weather and climate change also pose a threat, especially for large blues, which rely on flowering plants and ant nests for food.

The restoration initiative also benefited the tough oil beetle, the rock-rose pot beetle, the strident carder bumblebee, the downland villa, and the spotted bee flies.

Six organizations, including the National Trust, Somerset, and Gloucestershire Wildlife Trusts, J & F Clark Trust, Natural England, and Oxford University, manage or own the sites.