The British are remarkably lucky, lepidopterally speaking: some of the most common butterflies to frequent the country are staggeringly beautiful. The peacock, with its four spectacular “eyes” set on wings of velvet burgundy, is a glorious sight as it suns itself, wings held open. The modest common blue, sometimes seen in urban gardens, has a delicate upperwing the colour of an early summer sky, and an underwing speckled with dots and smudges, like characters in a yet-to-be-decoded language. Or there’s the painted lady – a large, handsome chequerboard of amber, chestnut and flecks of white. A migrant to British shores, it flies from southern Europe and north Africa each spring. These remarkable travellers are beginning to cross the English Channel now, the last leg of an epic, seemingly impossible journey. In the autumn, their progeny will fly back south.
But all is not well for British butterflies. Britain has – depending on how you count them – 58 species (compared with 2,500 or so of moths). Research conducted by the charity Butterfly Conservation has found that 24 of these are now threatened. The downward trend in numbers is long-term: a serious decline began to take hold after the second world war when intensive farming methods were adopted. Unpredictable, extreme weather patterns and the use of nitrate fertiliser (which encourages grass on farmland to grow thick and lush when butterflies often prefer it sparse and short) are also having an insidious effect.
Small tortoiseshells, with their orange wings flecked with yellow and black, and fringed with pale blue, were numerous 40 years ago, crowding thickly on buddleia blooms. But in the 1990s the population collapsed, a phenomenon connected with the arrival in Britain of a parasitic fly, Sturmia bella, which lays its eggs, like the small tortoiseshell itself, on nettle leaves. The caterpillars eat the flies’ eggs along with the greenery. The larvae then hatch from within the caterpillars’ guts and consume them from within, killing them. The arrival of Sturmia bella in Britain is probably a consequence of warming temperatures.
Of particular concern to experts at Butterfly Conservation is the fact that some species – including adonis blues, chalk hill blues and silver-spotted skippers, which diminished almost fatally in the early 1980s, but then responded well to efforts to restore habitats – have suffered setbacks over the past few years, putting them back on the vulnerable list. Conservationists are having to confront the fact that, in the context of the climate emergency, the methods they use to protect species may not work for long. The increasing extremity of the weather can seriously affect butterfly populations year by year. And however carefully habitat is conserved, if a population plummets, it can be difficult for it to recover when the butterflies are effectively corralled into isolated patches of protected habitat.
Butterflies are the tip of the iceberg, a tiny indicator of a catastrophe that the biologist Prof Dave Goulson has called the “insect apocalypse”. We need insects: they are pollinators, food for other animals and an essential part of the world’s functioning. Not for nothing is the ancient Greek word for the insect psyche. Which, literally translated, means “soul”.