Peter Frost reveals a secret ritual designed to enhance the survival chances of the rarest of butterflies.
At the end of July and for the early days of August something really unusual is happening in Fermyn Woods in the Rockingham Forest between Corby and Kettering in Northamptonshire.
Beneath the high trees, members of a quaintly named organisation called the Purple Empire arrange a special breakfast for some exotic and beautiful inhabitants.
Chief item on the menu will be shrimp paste and members of the Empire have scoured oriental supermarkets and food shops seeking out the most pungent and malodorous varieties.
So who is guest of honour at this morning feast? Why no one less than Britain’s second largest, and most spectacular butterfly — the aptly named Purple Emperor (Apatura iris). Only male butterflies are invited to the feast.
Spectacular the emperor might be, but it is also spectacularly difficult to observe. The colourful males flit high in the tree tops waiting to lure a dull female virgin to mate.
Generations of amateur but skilful lepidopterists have discovered the gloriously coloured male butterflies can be lured down, into camera range by, of all things, smelly and tasty shrimp paste.
There are several reasons why the Fermyn Woods are one of the best places to see this spectacular insect.
The woods are marshy and full of Goat Willow (Salix caprea) and Grey Willow (Salix cinerea) trees, the favourite food plants of the purple emperor’s caterpillars.
The other reason is the pioneering work by one of our greatest countryside writers and illustrators, Denys Watkins-Pitchford, who wrote wonderfully evocative country and children’s books under the pen-name BB.
Here is one of his wonderful scraper board illustrations
Like many other wildlife writers BB had realised the huge dangers of excessive usage of DDT and other insecticide sprays so common in the ’60s and ’70s.
He realised they were destroying species like the purple emperor as well as other insects, birds and animals further up the food chain.
Watkins-Pitchford had another far more intensely personal reason for his attitude to agricultural chemical abuse.
In 1974 his wife Cecily became unwell after working in their garden while a farmer was spraying his fields next door. She died a few weeks later.
In the very garden the couple had shared the writer built huge muslin cages where he bred the purple emperor, nicknamed “His Majesty” by butterfly fans. He bought the species back from the edge of extinction.
A male emperor is, without doubt one of the most elegant of all our butterflies. From some angles the wings look black with white bands — then as the sunlight catches the wing scales they light up with an amazing regal purple sheen.
The female is a deep brown and does not have any of the showy colour of the male.
If you want to spot an emperor the best time is early morning or in late afternoon. It is then that the males will occasionally flutter down to feed on animal dung, carrion, or even that tempting shrimp paste. This extra diet provides the emperor with much needed salts and minerals.
Males will sometimes spend over an hour feeding in the same place.
They are often found in woodland car parks landing on wet muddy cars.
Strangely they also enjoy sweaty humans and can often land on thrilled watchers to drink beads of salty perspiration.
Most of the time, however, they will be out of sight high in tree canopy feeding on aphid honeydew.
The males tend to congregate in very large oak trees they have used for generations. From such a high point, perhaps on the top of a hill, the males wait to pounce on passing females.
The males vying for the best and highest perches battle it out with purple wings flashing in the sun. It is a wildlife spectacular you will never forget.
When a dowdy virgin female flits by the pair fly off and settle high in the canopy to mate.
Mating over, she flies down to earth while he returns to his high emperor’s throne ready for another chance to pass on his DNA.
This article first appeared in the Morning Star 8 August 2014