More than 150 will be released across north-west England, where they have been extinct for a century.
More than 150 rare caterpillars hatched at Chester Zoo will be released into the wild in Manchester and Cheshire, their historic home range.
The large heath caterpillars were once common in north-west England, but have been extinct in the area for a century.
Conservationists at the zoo have been using fine art paintbrushes to move the tiny creatures, currently only a couple of millimetres long, into specially designed habitats at the zoo.
In partnership with the Lancashire Wildlife Trust, the caterpillars will be moved to the Astley Moss area of Manchester and Risley Moss in Warrington when they are fully grown.
Ben Baker, team manager of the zoo’s butterfly team, said: “Few people realise that the butterflies we might see in our gardens, forests and mosslands across the UK are heavily under threat, with many species disappearing from their last strongholds throughout England.
“The Chester Zoo butterfly team already cares for endangered and rare invertebrates from across the world, as well as these local butterflies. We are working extremely hard to stop these species from disappearing.
“It is an amazing privilege to play a part in embarking these rare caterpillars on their journey, returning the species to their historic home.
“Although minuscule in size at the moment, we’ll watch them grow and grow in our care over the course of the year, wishing them farewell in the spring.”
The butterfly can be identified by its orange wings, each bearing six black and white “eyespots” on the underside.
The species were once common across Britain, but over the last 200 years their habitats have been pushed further north.
Large colonies previously at home in Manchester and Liverpool have long since been lost to local extinction.
The breeding programme and reintroduction forms part of the Lancashire Wildlife Trust-led Manchester Mosses Species Reintroduction Project, which aims to return plants and insects to areas of conservation in Manchester, Cheshire and Lancashire.
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