Summer is in full swing at the moment (if you hadn’t noticed from the heat) and everyone in the ecology department is constantly busy surveying everything from crayfish to dormice to birds and plenty more. Much to my joy I have been tasked with a lot of the butterfly surveys on our sites and have had the pleasure of seeing an abundance of some of the UK’s most striking butterflies like the marbled white and the silver-washed fritillary and even some of the rarer species such as the white admiral. I have also been entrusted with surveying the illustrious purple emperor!

This elusive species has fascinated people for centuries and with good reason. To most, it is a magnificent butterfly just to behold. It is Britain’s second largest species, second only to the swallowtail, with a potential wingspan of 90mm and the male has a fantastic purple iridescence which gives the species its namesake. This aside however, it is also one of the most charismatic species in the UK due to its peculiar diet and weird and wonderful behaviour.

After emerging from their chrysalises around early July, individuals may travel up to a kilometre away from their breeding sites. The females will be in search of a mate and then suitable food plants for their caterpillars whilst the males will be in search of a suitably large tree from which to observe their empire. The males often spend their mornings patrolling local sallow trees searching for freshly emerged or roosting females, occasionally pausing for a meal to satisfy their unusual appetite. Rather than the nectar that other butterflies are often seen seeking, the purple emperor primarily feeds on aphid honeydew. However it is better known for its other, smellier sustenance which may include tree sap, animal droppings, carcasses or even human sweat all of which provide much needed salts and minerals that are otherwise absent in their diet.

In the afternoon they take up their throne upon the most prominent tree that they can find. Here they stand sentinel, primed to swoop down to waylay passing females or brawl with rival males. The males are truly aggressive and intimidating when defending territory and are even capable of chasing off small birds! Their reign is a dramatic but short lived affair and by August most of the adults will have died, leaving behind eggs that will spawn the next generation of monarchs in the following summer.

The butterfly’s odd behaviour is apparently infectious as it seems to inspire similarly bizarre reactions from the people that seek them. Throughout July, avid lepidopterists flock to southern England bearing gifts of the most rotten and foul smelling concoctions that they can create in the hopes that it will entice “His Majesty” down from his lofty throne in the tree tops. Just a few examples of the ingredients used in these nauseating cocktails are ripe cheese, roadkill, fermented fishpaste and even babies nappies! Many of these budding alchemists swear by their unique recipe as the only sure-fire way to coax the butterfly into making an appearance.

Sadly the season is soon coming to an end and we only have one survey left to go before we say goodbye to them for another year.  If you wish to catch a glimpse of this resplendent creature before they’re gone why not try inventing your own vile mix and paying a visit to one of their sites?