Monday, 23 July 2007

Emperor of our summer

To my mind, there is no British insect more impressive than his imperial majesty the purple emperor. Despite its large size, this magnificent butterfly remains an elusive prize for butterfly enthusiasts. It is on the wing from late June through into August but tends to spend most of the long summer days up in the canopy of mature oak woodland. Following many decades of steady decline the butterfly has disappeared from the handful of Norfolk and Suffolk woods where it had been previously reported. However, there are sites in Suffolk where the species has been reintroduced, thanks to the efforts of dedicated enthusiasts, and visits to these sites are often organised by Butterfly Conservation and local wildlife societies.

The stunning beauty of this butterfly is best appreciated at close quarters and, despite its arboreal tendencies, good views can be obtained when the males descend to the ground to probe for mineral salts, taken from the surface of forest tracks or animal dung. The males only do this occasionally and you stand your best chance by arriving early in the season, when the newly emerged males are in greatest need of the minerals. Early to mid-morning on a still warm day is best but nothing is guaranteed.

It is not only the size of the purple emperor that strikes you (they can attain a wingspan of nearly 10cm) but the marvellous purple sheen that adorns the upperwings of the male. This rich purple sheen appears to move across the wing as you change your angle of view. From certain angles it disappears altogether, leaving just the dark brown, almost black, ground colour and the white panels that, superficially, resemble those of the more common white admiral.

The allure of this butterfly has captured the hearts of many lepidopterists. Having encountered the emperor, some have gone on to devote incredible amounts of time to the study and pursuit of this butterfly. The great I. R. P. Heslop, who summarised years of research in his book ‘Notes and views of the purple emperor’, made a point of applying for teaching posts only at schools close to the southern oakwoods frequented by the species. Heslop had spent time in Africa where he hunted big game, including elephant, yet he wrote in his diary that ‘.. nothing in all my sporting or collecting career has ever given me so much joy as the seeing of my first purple emperor safely in the net..’ Fortunately, for the purple emperor, Heslop wasn’t simply interested in collecting; he also put his energies into discovering the life history of the species and into purchasing land to safeguard its future. Let us hope that more of our woodlands are soon graced by its presence.

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