Experts believe there may be only 400 slender Scotch burnets left in the British Isles, all of them living in six locations on Mull and Ulva, The Scotsman reports. The burnet lives on cliff edges in sheltered spots with its caterpillars feeding only on the birdsfoot trefoil.

"Like many really rare species, it is incredibly fussy," said Tom Prescott, a scientist with Butterfly Conservation, an environmental group trying to save the burnet.

The cotoneaster, a plant prized for its showy red berries, was brought to Mull for an estate garden and is now spreading out across the island, smothering everything in its path. Last weekend, volunteers worked to clear it out of a square-mile area.

Because of the burnet's taste for cliff edges, some of the clearing will have to be done by contractors trained to work from ropes.

Similar moths live in the Alps and Pyrenees, but scientists say the slender Scotch is a unique subspecies.