Declared extinct in Britain in 1979 before being reintroduced from European populations nearly 40 years ago, the large blue butterfly has recently experienced the most substantial reintroduction into the wild.
After five years of preparing the landscape for the species, 1,100 larvae of the large blue butterfly were released in Rodborough Common in Gloucestershire in 2019. One year later, an estimated 750 butterflies will have successfully emerged at the site.
Globally endangered, large blue butterflies’ life cycle involves the larvae tricking a particular species of red ant into carrying them into their nest. There, the caterpillars feed on ant grubs before emerging the next year as dusky blue butterflies with distinctive black spots on their wings.
As part of the effort, conservationists had to create the right conditions for the Myrmica sabuleti ant species and encourage the growth of wild thyme and marjoram, which the butterfly feeds and lays its eggs on.
The site had to also be prepared for them by creating small temporary grazing areas with electric fences to allow cows to graze slopes to provide the right conditions for the ants, while scrub control was also carried out.
Among Britain’s nine types of blue butterflies, the large blue species is the largest and rarest. The endangered species hadn’t been seen in Rodborough for 150 years, with the recent conservation effort marking the largest ever reintroduction in the UK.
