The stunning purple emperor butterfly is on the rise. But will it become a visitor to Derbyshire?
By now many of us will have celebrated the recent coronation of King Charles III, a historical event which we will remember for many years.
I’m sure many residents of our county will be looking forward to Charles’ first visit to Derbyshire since becoming King. However, personally, I think I would be far more excited if, during this summer, Derbyshire is graced with the appearance of the emperor, the most majestic and impressive of Europe's butterflies.
Purple emperors are definitely on the up in Britain, their range is slowly spreading north and their abundance is rising with each passing year.
These denizens of extensive, well-managed, broad-leafed woodlands are taking advantage of two things - global warming and an increased understanding of how to manage woods to their advantage.
The peak emperor watching period used to be early July until early August, but climate change has made it drift earlier and many Emperors can now be found gliding down the rides and glades in late June.
His imperial majesty is well named because he is the most impressive British butterfly one can find.
The male has the most gorgeous and flamboyant plum-purple sheen spreading across its upper wings. This is not achieved by a coloured pigment but by the refraction of light striking the thousands of wing scales.
This means that the iridescence is ephemeral - as you move, it moves and often disappears altogether until you subtly change your angle of view and it miraculously appears again.
Purple emperors are large, powerful butterflies which generally occur in low population densities in suitable woods.
The males have to be very vigilant when they need to find a female so they have adopted a strategy which sees them use one or more prominent, tall trees within the wood as lookout posts.
They can then sally forth to chase each other away and keep a lookout for any females gliding past.
Unfortunately this means that, unlike the majority of British butterfly watching, you often end up with a cricked neck as you spend hours looking through binoculars trying to spot the males perching high above you.
Most butterflies are nectar feeders, utilising flowers that are usually at ground level but a few, like his majesty, have adapted to feed on a sugary, amino acid-rich fluid which occurs high up in the canopy - honey dew.
However, this secretion is low in many minerals, particularly sodium, so the butterflies need to seek a secondary source, one that many of us will find distasteful - animal poo.
This penchant for smelly, mineral-rich poo is also the butterfly watchers salvation because the males descend down to the ground and, when they are actively feeding, become almost oblivious to someone carefully leaning over and excitedly taking of hundreds of images on their camera.
Some butterfly aficionados try to increase their chance of success by making special 'brews' to entice the insects down - the favourite at the moment appears to be a heady concoction containing rotten fish paste.
When the male emperors are seeking sodium they are incredibly indifferent to the presence of humans. I have witnessed them landing on people's shoes and even open hands - spending up to 15 minutes delighting in the salt-rich, dried sweat.
The butterfly has a very traditional life history. Eggs are laid in summer on sallow (a type of willow) and the caterpillars hatch a few weeks later, feeding slowly until the autumn when they start to hibernate for the winter.
They are now at their most vulnerable as small birds actively seek out hibernating insects as they forage through the cold days of winter.
Those that survive wake up the following April and during May they feed rapidly on the young sallow leaves. Once they are fully mature, they pupate into a well-camouflaged chrysalis and then finally emerge as adults a few weeks later.
His imperial majesty has not bred in Derbyshire yet, or at least not knowingly so. However, many experts believe that it is just a matter of time before he does.
The key in encouraging them is to make sure that our woodlands are well-managed for butterflies. The important factor which boosts the population of many woodland butterflies is the presence of lots of light hitting the forest floor.
In the past this would have occurred naturally by gales blowing down some mature trees, or the odd, natural fire.
However, today we try to mitigate against these so we need to replicate their effect. The simplest solution is to maintain really wide rides through the forest, rides so wide that they have an abundant low-level shrub layer on both sides, full of nectar-rich plants like bramble and privet. In the case of the purple emperor, these shrub layers need plenty of sallow bushes.
Another solution would be to re-establish coppicing so that there are blocks of different aged trees dotted through the forest.
Arguably one of the most impressive conservation projects in Britain to date is the rewilding scheme at Knepp, in Sussex.
READ MORE: Knepp Rewilding: the largest low-level rewilding project in Britain
Here a traditional farm has been allowed to return to a much wilder, nature-rich state, and it now has the largest population of purple emperors in the country.
In Derbyshire we need to provide wilder, more nature-rich woodlands and whilst we can't achieve this overnight, we can certainly make preparations to entice his imperial majesty to make a permanent abode in our county, and when that happens what a fantastic sight awaits us.
