A BUTTERFLY BEATING THE TREND

I mentioned the collapse of insect populations last week, but at least one butterfly seems to be having success. The purple emperor is a nymphalid (the same family as the red admiral, tortoiseshells and fritillaries). The adult males with wings open (centre) are especially beautiful as you can see, but the species is rare in Britain with a distribution focus of southern England. It can also be difficult to observe because it flies high among trees where it can find its food of sap and, where there are aphids, the honeydew they exude.

Whilst this magnificent butterfly flies high in the tree-tops of well-wooded landscapes in central-southern England they do descend to the ground sometimes where the males, in particular, search for salts on roadkill, other dead animals, cowpats or other dung.  Where there’s muck there’s beauty, to misquote the famous phrase! The Victorians used all sorts of ruses to attract them down to the ground, including soiled nappies and smelly cheese!

This butterfly has been in decline in Britain throughout the twentieth century. The best site for it is the Knepp where Isabella Tree and Charlie Burrell have created their famous rewilding project that some of you may have visited, or read their book. In the summer this year, on July 1^st, their ecologists recorded 283 purple emperors! There have been good records elsewhere, too. The long, hot summer has probably had much to do with it as well as our warming climate generally; only time will tell if this is a long term trend but it augurs well.

The purple emperor females place their ova singly on the upperside of the foodplant (usually sallow/goat willow Salix caprea or sometimes other willow species). Eggs hatch in about ten days and the caterpillars feed until their second moult when they hibernate on a twig of the foodplant until the next April. The larvae grow an impressive pair of “horns” which they wave about aggressively in defence if disturbed. They pupate hanging upside down from a leaf, displaying excellent camouflage.

The imago (adult butterfly) emerges from the pupa around the middle of June. The whole life cycle of this butterfly is fascinating and I recommend you read about it in full at https://ukbutterflies.co.uk/species.php?species=iris where UK Butterflies provide a wealth of detailed information on the life cycle.

Betts Ecology do much to provide and protect butterfly habitat and we are always interested to hear of your sightings.

TO INSIGHT READERS

Please note that this will be the last Insight item from me for a while as I am retiring, although I still hope to contribute items occasionally. I have greatly appreciated researching all the varied topics and hope you have enjoyed at least a few of them. Thank you all for reading them. CJB