For once PETER FROST, who too often finds reporting on the state of the British countryside’s fauna and flora to be an act of depressing despair, feels almost elated.
All too often my Ramblings are about bad news in the countryside — threatened species, loss of habitat, shooting and hunting interests getting more and more influence with government and Defra, rare animals being shot or culled, rare insects being poisoned by agricultural chemicals.
Now, however, cheerfully fluttering into this week’s column is a huge blue butterfly — nearly two inches in wingspan — which, although declared extinct in 1979, is being seen this summer in bigger numbers than ever before in Gloucestershire and Somerset and some other locations.
Although overall butterfly populations have slumped across the country this year because of the wet weather, the Large Blue (phengeris arion) is doing really well after it has been brought back from the dead through the dedication of several conservation organisations and many individuals.
This is the largest and rarest of all our blue butterflies — distinguished by the unmistakable row of black spots on its upper forewing while the undersides are pale brown with black spots.
This butterfly was first recorded as a British species in 1795 and, even then, was considered a rare beast.
Due to the loss of suitable habitat, our particular Large Blue became extinct in the British Isles in 1979 when the last one had been seen fluttering across Dartmoor in Devon.
The Large Blue then became the subject of a highly organised reintroduction programme using stock from Sweden. The success of this enterprise is made even more remarmkable when one considers its elaborate life cycle.
The larva (below) is parasitic. It feeds on the grubs of a red ant, Myrmica sabuleti, on which its existence depends. Although this reliance on ants had been known for many years, the fact that it is a single species of ant was unknown to conservationists for many years until discovered in the late 1970s.
Unfortunately, the discovery came too late to save the native population. Today’s reintroduction efforts combine its focus on the populations of the ant as much as that of Large Blue itself.
If the Large Blue’s success continues, Britain’s most endangered butterfly could soon return to its pre-extinction numbers and be removed from the International Union for the Conservation of Nature red list of threatened species. It is the only butterfly in Britain on the list.
Since its re-introduction from Sweden in 1984 it is now found in higher concentrations in south-west England than anywhere else in the world, particularly at the Gloucestershire Wildlife Trust’s Daneway Banks and Somerset Wildlife Trust’s Green Down, where decades of grassland management have encouraged thyme and marjoram — plants that play an important part in the butterfly’s complicated life cycle.
Some 10,000 have already been recorded at these two reserves this year an estimated 60 per cent of Britain’s entire population. They have laid more than a quarter of a million eggs.
Overall their population in Britain has reached about 17,000 at 50 different sites.
One of the best places — with good public access — to see the Large Blue is the National Trust property at Collard Hill (below) near Street in Somerset. Specialist rangers are there on some days to help visitors make the most of the stay (www.nationaltrust.org.uk).
The butterfly’s recovery is a triumph for conservationists and their discovery of its sneaky, very complicated and devious life cycle.
A bit like a cuckoo in the nest, the butterfly’s caterpillars spend three weeks feeding on thyme and marjoram before emitting scents and sounds that trick the ants into thinking they are its own grubs.
The deceived ants then carefully transport the caterpillars into their underground nests to rear them in safety. Rather ungratefully the caterpillars reward their hosts by feeding on the ant’s own grubs for 10 months before pupating the following year and crawling above ground to emerge as a beautiful blue butterfly.
The beautiful adult will only last a few weeks as it lays its eggs on the flower-heads of wild thyme and marjoram. To encourage both the food plants and the ant’s nests requires scrub clearance and careful grazing of the wildflower-rich grassland on the reserves.
All this conservation work has a bonus as the special management also helps a huge diversity of wild plants and other insects to thrive. They include Meadow Brown and Marbled White butterflies, scarce fly orchid, frog orchid and musk orchids, and the Downland Villa bee fly which disappeared from view for 50 years before being discovered again in 2000.
One impressive measure of this conservation work is that at Green Down in Somerset Meadow Brown and Marbled White butterflies have had their highest and second highest numbers respectively since records began.
Mark Green, the reserves manager for Somerset Wildlife Trust told us: “The amazing numbers of Large Blues recorded this year show what can be achieved through close partnership working and landscape scale conservation land management, underpinned by sound science.”
This blue butterfly flitting across our countryside is a powerful symbol of what can be achieved in preserving and conserving our native flora and fauna when good intentions replace profit as the main motive for changes to the countryside.
However, we cannot afford to be complacent as numbers of the Small Tortoiseshell butterfly (Aglais urticae) (above) — which is one of the most recognisable and widespread in the country — appear to have plummeted this summer. Populations of this commonly seen garden butterfly have fallen by 73 per cent since the 1970s.
This article first appeared in the Morning Star 2 September 2016 .