What gorgeous creatures our moths can be

Another Life:On a calm night between storms, five little moths came to rest upon the glass of our uncurtained living-room window, spaced out like a squadron of fighter planes. Their undersides made them even more anonymous than usual, but size suggested the winter moth, Operophtera brumata, one of a handful of species likely to be on the wing at the turn of the year.

Looking it up in the majestic new paperback from the Ulster Museum, The Butterflies and Moths of Northern Ireland, I found that even Robert Thompson's magical camera could find nothing very special in the winter moth's brown plumage - except, as so often happens in his pictures, that it might feel very nice to stroke. But from there, of course, I was drawn on through the book's remarkable gallery.

Together with another massive tome on Ireland's dragonflies (also a collaboration by Thompson and Ulster Museum entomologist Brian Nelson) it offers a wholly fresh and dazzling view of Irish insects. You'd have to go back to the best-selling popular guides of Victorian natural history to find anything more prompting of wonder. The book had to wait on today's camera and print technology, for the knowledge and skill of a particular naturalist-photographer, and for the willingness to spend public money on a great PR job for one essential branch of Ireland's biodiversity.

Butterflies and moths get their ecological importance from the huge range of trees and plants their larvae use for food. To keep an eye on them and their caterpillars is to look out for the welfare of a multitude of other insect groups and also their predators - birds, bats and even fish.

While Ireland's resident butterflies number a mere 29, the island's moths total 528 - and that's just the "larger" ones.

The bulk of the book, therefore, is taken up by accounts of the 462 moths so far recorded in Northern Ireland (a good many of which are in decline) and the maps of their records. A section on habitats reminds us how little of the lowland north remains at all wild, and how closely conserved are the remnants of broadleaf woodland, bog and undisturbed sand dunes. The book also tempts more amateur enthusiasts with its details of light traps, pheromone attractants, camera gear and techniques.

My overriding delight with it, however, is unashamedly aesthetic - what gorgeous creatures moths can be! The butterflies we knew about, even if Thompson finds fresh ways to flatter them, but the moths are something else.

He couldn't hope to find all of them, but their sumptuous colours, textures and designs often ravish the eye like the best fashion photography.

They also amount, in very many species, to a "cryptic" patterning that matches wings closely to lichens, leaves and bark and breaks up their shapes like army camouflage. The photograph shown on the right is chosen to let you spot the moth in question - the reportedly "scarce" Merveille du Jour, found on a lichen-crusted branch on Rehaghy Mountain in Co Tyrone. Other examples could send you cross-eyed with the effort to spot the moth.

This marvellous camouflage is the product of natural selection, as mutations of wing-colouring and pattern interact with predation by birds and bats. The more cryptic variations have let more moths survive from one generation to the next, thus progressively selecting out the genes for an optimally cryptic appearance.

The patterning of one Irish species, indeed - the peppered moth, Biston betularia - has become a classic demonstration of evolution by natural selection. In woodland with clean air, the moth comes in various shades of grey, mixing light-grey scales with black ones. In the mid-19th century, a coal-black specimen was collected near smoky Manchester, and by 1950 more than 90 per cent of these moths in the area, along with some birds and other insects, were showing dark forms of "industrial melanism".

Similar examples were found around America's industrial cities, together with a comparable reduction in melanism as industry cleaned up its smoke. In the widely employed classic theory, the darker forms evolved because, as lichens died from air pollution and bare tree-bark turned black, the paler peppered moths were more obvious to birds and only darker mutations survived. Modern scientists have some problems with this story, but nothing likely to comfort the proponents of "intelligent design" (see www.arn.org/docs/wells/jw_pepmoth.htm for an excellent read).

If there's a flaw in The Butterflies and Moths of Northern Ireland it's in the book's somewhat cloistered regionalism. Its predecessor drew on an island-wide survey of dragonflies, involving a wide range of scientific and amateur recorders. This book relies on records within Northern Ireland, with only occasional (and sometimes confusing) references to Ireland as a whole. Fortunately, its seductive images should help to foster the growing enthusiasm for moths on both sides of a most unnatural border.

The Butterflies and Moths of Northern Ireland, by Robert Thompson and Brian Nelson is available from www.blackstaffpress.com for €35 with €12.33 postage