Rejoice and be of good cheer! Despite a generally low adult emergence and a lot of grotty flight season weather, the Purple Emperor has managed to lay a goodly number of eggs, and larvae are in reasonable numbers this autumn.
I haven't quite finished my annual standardised count of autumn larvae in Savernake Forest, but it is already clear that 2021 will be the fifth best year in a 13 year sequence there. Here's the data -
2009 = 141 2014 = 24 2019 = 16
2010 = 59 2015 = 20 2020 = 12
2011 = 21 2016 = 17 2021 = E40*
2012 = 22 2017 = 18
2013 = 190 2018 = 76
* E = estimate
Numbers seem relatively high elsewhere, though larvae are patchy. Also, tits are down - they had a rotten breeding season due to the cold April and wet May.
All this suggests that 2022 could be a good Emperor year - only we need a cold winter, a non-early spring, and good weather during the pupal period (the worry here is that we are due a Platinum Jubilee in June, and the track record of weather during Royal Jubilees is nothing short of appalling...).
And larvae are running late. This year I found a 2nd instar larva at the start of October, in Glos, by far the latest record of the L2 stage. This is not a concern; they'll catch up, as sallow foliage is in good condition this autumn (though Sallow Mildew is prolific on overhung sallows).