Of course, the weather falls apart as soon as the Duke of Burgundy starts to emerge...
The butterfly will be at peak season at many of its sites in southern England over the Bank Holiday weekend and early next week. They have had a difficult time with the weather lately, but as yet they haven't had more than they can't cope with inflicted on them, and there will be many more adults to emerge at most sites.
News from various places -
Noar Hill. It started here remarkably early, on April 8th. I visited in marginal weather conditions on April 23rd (St George) and was impressed by the condition of the habitat. The site was looking the best its looked for this species for many years: rabbits were almost absent, the turf height was ideal, cowslips were fairly abundant, and the wildlife trust had scaled back on scrub cutting. The butterfly may well start to go over here soon though. Here's a nice view of the site -
Ivinghoe. A top site in the north Chilterns (NT), holding a scatter of colonies along the west-facing slope down to the mouth of Incombe Hole. Visited in marginal conditions on April 29th and counted 20 Dukes, but might have doubled that tally had the weather been better. Habitat conditions were excellent over much of the slope, though the slopes of Steps Hill were a little on the short side. The slopes are managed firmly with this butterfly in mind. Here's the main male lek, where about ten can be seen in good weather at peak season -
Good news from the re-introduced colonies in the Bradenham Valley (NT) west of High Wycombe. Viable numbers have been seen at both sites (Park Wood and Small Dean Bank) and more must be due to emerge there - news per Ched George.
Back in the Cotswolds, where Natural England is funding a major survey and ecological study (through Dave Simcox), the butterfly seems to be holding back, waiting for the weather to improve before emerging properly. Certainly it is by no means well out on Rodborough Common (NT), Stroud, yet (and Pearl-bordered Fritillary has yet to start in Cirencester Park Woods).
This butterfly needs ten good days at the start of May. Hopefully that's not too much to ask....