The Large Blue butterfly - raised by ants!
One of Britain's most beautiful native butterflies - recently brought back from extinction - the Large Blue, has a bizarre life story that involves getting itself adopted by ants whilst a caterpillar. Evolution has equipped the butterfly to fool the ants into looking after it. But some ants seem to be getting wise to what's happening...
From the 1790s, when the butterfly was first documented as British by William Lewin, this enigmatic species was prized by collectors due to its great beauty and rarity. Frustratingly to them, they were unable to procure perfect specimens as it proved impossible to rear them in captivity - the caterpillars always dying when they were about three weeks old.
The reason was found in the early 1900s. It was discovered that after feeding on the flowers of wild thyme for three weeks, the caterpillars fell to the ground. Here they were found by red ants, which picked up the caterpillars and took them into their underground nest, where they were placed in the brood chamber. The caterpillar spent the next 10 months feeding on ant grubs before pupating to a chrysalis, and then emerging as a butterfly the following year.
It was eventually discovered that the Large Blue caterpillar secretes a chemical signature that fools ants into thinking it is one of their grubs and taking it back to their nest and feeding it - often with more attention than to their other offspring, presumably because it is so large and impressive.
Owing to the difficulty of maintaining ant nests in captivity, naturalists were unable to halt a decline of the butterfly. By 1950 the Large Blue occupied only 25 sites, which rapidly declined to two by 1972. By 1979 it was extinct in Britain.
Though several ant species have learned to see through the adoption ploy, scientists have found out which are still susceptible to the parasitic behaviour, and this has helped them them bring the butterflies back from extinction in Britain. This was done by Natural England and the Centre for Ecology & Hydrology, on a former site in Dartmoor owned by the National Trust. They recreated the precise conditions that support this particular ant, and by 1985, had re-introduced Large Blue butterflies to the south west of England.
Further reading
Links to external websites are not maintained by Bite Sized Britain. They are provided to give users access to additional information. Bite Sized Britain is not responsible for the content of these external websites.