Those of us in Norfolk, even with a passing interest in the natural world, are aware of the swallowtail, the UK’s largest butterfly and the jewel in the crown of Norfolk’s wildlife. Historical records suggest it was formerly known as ‘King William’ then latterly renamed ‘The Queen’. Despite settling to ‘Swallowtail’ it retained its regal status and has reigned supreme

Purple Emperor butterfly, photo by Robin Chittenden

over the Broads. Then, last year, its eminence was usurped by a higher-ranking monarch, the purple emperor.    

After an absence of more than forty years this magnificent butterfly has returned to its former realm. During July 2017 two were spotted in Sheringham Country Park and a few days later a female was photographed at Beeston Common. The purple emperor has never been numerous or widespread but, prior to its disappearance in the 1970s, it did have a strong foothold in Norfolk. Even up until the 1950s it was recorded at most suitable woodlands across the county, including Norfolk Wildlife Trust’s Foxley Wood and surprisingly, NWT Hickling Broad.

Since ancient times purple has been the chosen colour of royalty and the male emperor does not disappoint. The iridescent wings shimmer as the butterfly skips through dappled sunlight, switching back and forth from a brown hue to electric purple. The female lacks this sheen but is still a stunning insect with both sexes having a band of white across the forewing. The underwing is also attractive, combining a mixture of orange, grey and brown with a black and orange ‘eye-spot’ to startle any prospective predators.   
    

Oak tree, photo by Yvonne Seaman

Despite being Britain’s second largest butterfly, the purple emperor is not easy to find. It never nectars on flowers and spends most of the day sitting high up on its oak ‘Master Tree’ throne feeding idly on aphid honeydew. However, they will patrol nearby clearings waiting for a passing female. The male will then jealously guard his empress, gliding in escort behind her; they will then search for a suitable patch of sallow or grey willow for her to lay eggs. Like the over indulgence of emperor’s courts in the past, mating can take up to three hours and both will copulate with multiple individuals.

In ten or so days, a small brown caterpillar emerges. After consuming the remains of the egg shell, it then feeds voraciously on the sallow leaves until November, when it then hibernates; it resumes feeding in the spring. The caterpillar is well camouflaged, as it grows it becomes green with yellow strips, and has a passing resemblance to a slug with antennae like projections sticking out from the side of its head.

The male butterflies have the unusual habit of being attracted to shiny objects and have been coaxed down from the tree tops by reflecting mirrors or other glittery objects. Although, the best chance of seeing purple emperors is in late morning when they descend to drink or search for mineral salts from mud or animal faeces. Unfortunately, many people’s first view of an emperor is watching it crawling over another animal’s poo!   
 
With increasing records in nearby Cambridgeshire, sightings in Norfolk may become more frequent, with July and August being the peak months.  In our ever-fragmenting countryside it is increasingly important to create wildlife corridors as part of a Living Landscape to allow the return of species such as the purple emperor. Many of our butterflies have been in steady decline, although some promising population growth has occurred recently. Norfolk Wildlife Trust works hard to ensure our woods, heaths and wetlands are in as favourable condition as possible.   
                         
Hopefully this isn’t a ‘purple patch’, but the start of a long-term colonisation by this glorious sovereign.  

Robert Morgan Assistant Reserves Manager (Broads South)
Header photo by Robin Chittenden

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