This blog / website has received >10,000 hits so far this month! A fact that speaks volumes for the cultural significance of this butterfly... Clearly, Purple Emperor spotting should become an Olympic event.
Yesterday, Tues 26th, Neil Hulme was touring Fermyn Woods on his Japanese folding cycle. He saw 13 males down on the ground, only one of which was pristine - suggesting that the male emergence there is all but complete. He failed to see Herself (though the technique for spotting females is different to those for spotting males).
In Warwickshire, the butterfly started in Oversley Wood, on the 17th and in Ryton & Wappenbury Woods on the 22nd. These introduced populations are doing really well, and studying their spread is really helping our understanding of the insect's powers of colonisation.
The overall picture is that iris has emerged in reasonable numbers at most of its sites except in West Sussex where it has clearly crashed. Away from Sussex (and as close to Sussex as Bookham Common, Surrey, and Alice Holt, E Hants) numbers in the better colonies are 'average' or even 'quite good', though some smaller colonies seem only to have appeared in low numbers.
Also, this is an old fashioned season in terms of time of emergence. The butterflies held back from emergence, waiting for the weather to improve. Back in the 60s and 70s the butterflies often didn't appear until mid July (with exceptions like 1970 and 1976).
The butterfly is now at peak season generally. Males will soon start to get tatty and faded. The coming weekend is really your last chance to see the males in good condition, though the butterflies will last into mid August at many sites this year.