I've come across the Purple Empire having thought I saw an Emperor in our wood last weekend.
We own a 4 acre chunk of Gayhurst wood near to Newport Pagnel in Buckinghamshire. It is plantation woodland about 25 years old on an ancient woodland site. The plantings are mainly spruce, pine, ash and oak but includes a small proportion of sallows along with alder and field maple.
I have to confess that the sallows were low on my interest list and I'd planned to coppice some of them to let some light in & encourage some young growth. Then, last weekend, I entirely failed to get a good look at a large black butterfly with a white band which shot by at speed. Size, speed and the glimpse I got suggest that it could only really be a Purple Emperor which I'm pleased as punch about.
Clearly the presence of Emperors will change my planned management of the sallows - both limiting any cutting and keeping them in some degree of shade.
I'll keep looking and see if I can spot more adults, then have a search for larvae in a few weeks.
I was interested to see that one of your contributors has been finding Emperors at Finemere which is only about 10 miles from us and I think BBOWT have them in Little Linford Wood just over the M1. Given their speed I would imagine they have the potential to travel some distance.
Anyway, I'll let you know if I find any more adults and also whether I am successful in finding larvae.
Many thanks for such an informative and entertaining web site.
All the best