July is the perfect time to look for butterflies and we’re spoilt with so many wonderful species in Gloucestershire. One of the most wonderful, in story as well as appearance, is the large blue butterfly. Despite its name, it is by no means a giant. With a wingspan of up to 44mm, this little insect is a delight to behold. Its vivid blue hue, black outline and row of black spots across the upper wings make it distinguishable from its smaller counterparts. It is a true asset and heart-warming success story for our county.

One of Gloucestershire’s most prized possessions

Declared extinct in Britain in 1979, the large blue is now one of Gloucestershire’s most prized poss-essions. Its reintroduction to just two sites in the country – Daneway Banks in the Golden Valley and Dartmoor in Devon – proved successful thanks to the hard work and dedication of a number of butterfly experts, vol-unteers and organisations including Gloucestershire Wildlife Trust and Butterfly Conservation, with support from Grundon Waste Management.

The butterfly’s extinction was extremely frustrating for conservationists, as it wasn’t a decline that had gone unnoticed. For many years specialists had studied the large blue and failed to reach a conclusion as to why it was suffering. Break through studies revealed that it was the gruesome nature of the insect’s life cycle that was the key to its survival.

It cunningly fools the red ants into ‘adopting it’

Once hatched, the large blue starts life as larvae, feeding on the flower heads of wild thyme and marjoram. After this period the caterpillars drop to the ground, where they are discovered by a very particular type of red ant (Myrmica sabuleti). The caterpillar cunningly fools the ants into ‘adopting it’ and carrying it to their nest. There it feasts on the young grubs for almost a year. After pupating, it emerges from the brood chamber as an adult to find a mate.

The discovery of this very complex life cycle meant that scientists could solve the mystery of its decline. It showed the large blue needs wild thyme, populations of the red ant to be present, and a short turf in order to survive. This information enabled individuals and organisations to ensure these exacting factors were present at reintroduction sites.

Its reintroduction has been a great success

Sample stock of the butterflies were selected from Scandinavia and carefully reintroduced at Daneway Banks in 2000. Through careful land management, specialised grazing methods, and meticulous surveying, the reintroduction has been a success, with the large blue flourishing at the site near Sapperton, Gloucestershire. Over 2000 were seen flying in June 2014 and the first adult of 2016 was reported on 5th June.

The large blue will continue to fly until mid-July and I would urge anyone with an interest to seek it out, as a really rare and special species – not to mention a huge success story for the county of Gloucestershire and conservation as a whole.