Spent a magical two hours in Savernake Forest today, watching a full-fed Purple Emperor larva on walkabout, looking for somewhere to pupate. This was No 198, who was initially found on Nov 10th. He over-wintered on the underside of a branch junction over 4m from where he had been feeding in the autumn, matching the colour of the bark perfectly, chameleon-like. He came out of hibernation at the start of April, but then disappeared, only to reappear two weeks later, bright green and feeding happily some 4.5m away - not bad for a caterpillar about 1cm long! He then fed up in that general vicinity, on a late-leafing tree.
But today was his Big Day: he was full grown, and was turning pale - a sure sign of a Purple Emperor larva ready to pupate. Today, I arrived at 1.10 to check him, and No 77 who lives close by on the same old gnarled sallow tree. No 77 was sitting on his favourite leaf, comatose, and remained so throughout. He'll go off to pupate soon. But at 1.15 No 198 he suddenly crawled off his seat leaf and began crawling up stem.
All told, he covered a distance of some 16m, including U-turns down dead branches, in 1hr 45 mins. He was travelling at a speed of 13m per hour, and measures 6-7cm in length. If disturbed he'd freeze. When crawling on the branches, he constantly waved his head from side to side, as if searching and testing. After 40 mins he encountered his first leaf, tested its underside but rejected it.
Finally, he settled on the underside of the 7th leaf he encountered, a large one in a very leafy spot, and spun some silk there (PE larvae are serial spinners of silk). Hopefully he'll pupate there, hooking on to a silk pad, though he might just have been resting. We'll see...
He are some photos of No 198's Great & Wonderful journey -
Whatever mistakes you make in life Never Underestimate a Caterpillar (Erucam Nunquam minoris Aestomate)