RECORDS were broken recently by the Purple Emperor butterfly. One was seen to emerge from the chrysalis on June 16 in Savernake Forest in Wiltshire, a fortnight early. The earliest ever recorded by Richard South in his monumental work: British Butterflies published in 1906 was June 24.
He said that was an extraordinary date. The usual date in the woods where I live has always been July 4, but in the drought year of 1976 one did exceptionally emerge on June 30, though never again.
This magnificent insect , which has gripped the imagination of entomologists and collectors for 25 years is only found in Surrey, Sussex, Hampshire and Wiltshire and then only in scattered populations in ancient oak forests. It is one of our largest butterflies and certainly the most difficult to see as it spends most is its short aerial life as a flying insect on the crowns of large oaks. This emperor of the forest does have unfortunate habits at times, which is what has caused its downfall.
When newly emerged, like many butterflies, it requires special foods to complete its growth. Minerals are found in all manner of weird objects from dry creosote, sump oil, or human faeces. I have known a newly emerged emperor to spend three hours finding trace elements in plastic downpipes. Others I have often seen sucking juices from squashed insects on car radiators. In the past they have often come into my kitchen and all but drowned in the sink of washing up water when my back was turned,
Last year an emperor found my sweaty sandals to its liking and spend the first five minutes of its life drinking up whatever traces it had found on the sandal strap, or even what I had stepped on out in the woods.
After this brief encounter with the underworld, the monarch of the woods takes to the highest trees, where the couples engage on wild circular flights of courtship well out of reach of humans. Every forest has its traditional courtship tree where twenty or more of this royal family have sorted out who belongs to whom. Once engaged, the couples then go off together and after mating, the female searches for the best looking willow tree where she will lay her eggs.
Her caterpillars gradually grow, hibernate during the winter, then start eating the leaves again in the spring ready to pupate. Their life is therefore of one year exactly, but as adults with wings, only ten days. In South’s day, a century ago, the usual date for emergence was July 15 or even as late as early August. This season I saw my first one in the garden on July 1. This year it did not come down to see us, but stayed more or less asleep all day at the tip of an ash branch high above the kitchen door.