A heads up to say that His Gloriousness should be making a spectacular appearance in the second episode of BBC1's new blockbuster of British wildlife, on Sun March 19th, the Woodlands episode.
Footage was filmed at Knepp.
Look out for the swallow-chasing sequence... ... ... That's my butterfly...
(assuming it made the cut, and I'll dispatch an entire battalion of Sussex Emperors to smash up Broadcasting House if it didn't...).
Rejoice and be of good cheer! Purple Emperor caterpillars are surviving the winter unusually well.
Incredibly, all of the eight I've been diligently following in Cirencester Park Woods, Glos, have survived the meteorological winter. I've never got into March unscathed before...
Also, Ben Greenaway still has 12 of the 20 he's been following in Southwater Woods, up the road from Knepp in W Sussex. That's good by his standard.
I haven't checked the few I've got in Savernake Forest for a while, but will soon.
So, it looks as though predation rates are unusually low this winter, though winter is far from over yet...
This could make up a bit for the poor egg lay caused by last July's extreme heat, and the loss of many eggs and young larvae in the heatwaves...
Here's the head of Boris The Third, photographed in CPW by Andrew Fusek-Peters on Wednesday. I hadn't realised how warty they are -
Welcome to Emperoring in 2023... This is, by the way, my 60th year of butterflying (I started late, having wasted time birding...).
The good(ish) news is that Purple Emperor larvae seem to be overwintering quite well. I have lost none to predation at my local study site, though only with a modest sample; and none in Savernake Forest (small sample), where losses are normally high.
However, I have lost four out of five at my Lambourn study site. I'm not sure why losses are so high there. I'm not even sure what constitutes a viable sample... The more I study this butterfly, the less I understand it...
Just up from Knepp in West Sussex, Ben Greenaway has lost only six out of 20, which isn't too bad.
However, February and early March constitutes the crunch time (pardon the pun...).
Fingers crossed...
Here are some of my babies -
'Boris the 3rd', in a branch fork
Happy New Year to all of Purple disposition...
I'd like to say that the prospects of an annus mirabilis year for the Purple Emperor are looking good, but they're not - at least, not at this stage.
Autumn larvae were scarce everywhere. We think because 1) the egg lay was low, due to females being stressed by extreme heat; 2) many eggs failed to hatch - they boiled in the bag instead [as happened in Sherwood Forest]; 3) many young (L1) larvae desiccated in the mid-July and early August heatwaves [as has happened before, e.g. in 1976 & 1989].
In Savernake Forest, Wiltshire, autumn larvae were at the second lowest level I've recorded in 14 years of standardised searching. On the Lambourn Downs, SW Oxon, autumn larvae were a third of previous levels (it's a Year 4 study site). In Cirencester Park Woods, Glos, (a new colonisation, in Year 2), larval numbers were down by 50%. And I've searched assiduously in all these sites.
And the big one, Ben Greenaway has found that larvae are 50% down in his major study area just up the road from Knepp in W Sussex (though in part due to habitat deterioration).
In addition, I noted a severe paucity of the sallow-feeding moth and sawfly larvae I find in the autumn, as bycatch, everywhere. There seems to have been a mass failure of things like Pebble Prominent (which has distinctive larval feeding marks).
That's the bad news...
The good news, is that Great Tit numbers appear to be well down. They, and other titmice, seem to have suffered from the cold spring and, possibly / probably the impact of the heatwaves on insect food sources. Great Tits are major predators of hibernating Emperor larvae. I'm trying to get some info from the ornithologists on this... (Bird Garden Birdwatch should provide a good pointer).
Also, the severe cold snap in early December should have taken out various invertebrate predators which thrive in mild winters.
So, there is Hope...
Other key life stages determining adult numbers are the pupation period and pupal period, which we're just starting to study properly. There seem to be major losses during these stages, suggesting that the shorter time the insect spends pupating and as pupa, the more Emperors fly. 2022 had poor weather during that period (remember the Jubilee downpours).
One prediction I will make, is that the 2023 Purple Emperor season is unlikely to start before Midsummer Day (unless we get a long fine spring and a wonderful June) - because the sallows will over-flower next spring, and leaf late, in response to heat & drought stress.
Here's Larry The Cat(erpillar), one of 8 I'm following locally -
My annual searches for autumn larvae are now complete. Larvae have been unusually - and worryingly - hard to find.
For the last 14 autumns I have searched diligently, in a standardised manner, for larvae in Savernake Forest, Wiltshire. Larvae have been relatively numerous after all previous hot summers, and I was expecting to find them with some ease this autumn.
However, 2022 has been the second poorest autumn on record for larvae in Savernake, after 2020 (which saw an old fashioned wet July).
The same picture has been presented at my other monitoring sites, near Lambourn and in Cirencester Park Woods, Glos (a new colonisation).
It appears that something went badly wrong, something outside my previous experience - outside my box.
However, my searches are from the ground (I can no longer climb sallows due to arthritic knees) and my findings are based on the assumption that the females lay the same percentage of eggs low down each year - for which there's no evidence either way...
Much depends on the Dangle Leaf season, now starting. I find this method about as effective as Floo Powder in Harry Potter, though it works well for Ben Greenaway on small-leaved sallows in Southwater Woods, W Sussex. The dangles blow off on my large-leaved sallows (last late November, Storm Arwen took the lot...). Ben is only just starting his searches now.
Worse, every early November I pray in earnest for cold, wet, miserable weather. This is the time when larvae are going into hibernation (diapause). They don't go far when the weather's poor. But wander far and wide in mild weather. Yet again, the weather's set to unseasonably mild during this crucial period.
A few larvae are already in hibernation, but the sallow leaves are staying on well in the absence of frosts.
Here's 'Cruella', in hibernation on Sun Nov 6th:-
Watch this space...
I am still more than struggling to find Emperor larvae this autumn, finding one for every 2 hours 30 mins of actual leaf searching - that's as bad a find rate as after a cold, wet summer. This is in the S Glos / N Wilts / SW Oxon region which was not drought affected and where very few sallows dropped leaves. Sallow foliage conditions there are Very Good.
I am also finding precious little else: hardly any of the moth larvae I normally find at this time of year (e.g. Buff Tip, Clouded Border, Pale Tussock, Pebble Prominent, Swallow Prominent). Yesterday, at last, I found the first batch of larvae of the sallow foliage-feeding sawflies normally encountered whilst searching sallows in autumn (this one is probably the common sallow-feeder Euura pavida) -
One theory is that the egg lay was not poor, but that there was a high failure rate of baby L1 larvae - as can happen in heatwaves (I first noted this in 1976), coupled with hatched egg cases falling off the leaves.
Such losses leave no tell-tale signs, whereas the vacant seat pad and old feeding leaves of predated L2 larvae are quite prominent (and have been diligently recorded by me each autumn).
This is tricky. I have no experience of eggs (hatched or unhatched) coming unstuck, but of the paltry nine larvae I have found so far this autumn the egg case base was present in only three instances - that's unusually low and may suggest that eggs (hatched or unhatched) might have come adrift in the hot weather.
The show continues - I need a bigger sample, and I should eventually make some sense of the situation. It's not critical (at least away from the drought-struck South East, where it might be) but it is deeply concerning, and is totally outside my experience. As Fred Trueman used to bemoan on Test Match Special, usually when England were leaking runs through an untenanted third man boundary: "I don't know what's going off out there anymore!"
I have yet to find any sign of Emperor larvae or eggs in Hailey Wood, Cirencester Park Woods - my local wood, where I followed and chronicled the likes of 'Boris', 'Jacob', 'Rishi', 'Priti' etc. earlier this year. Nothing, and I'm keeping a keen eye open for egg case bases and vacant leaves from failed L2 larvae.
The results of my annual stratified random sampling for PE larvae in Savernake Forest will be particularly interesting. I've carried this out there each autumn since 2009.
This early autumn I am finding Purple Emperor larvae at the rate of one every 2 hours 30 mins, searching as usual in Wilts, Oxon and Glos. That's extremely poor, and it looks as though something has gone very badly wrong. Larvae are as scarce as after wet and windy flight seasons, or scarcer.
In all previous autumns after hot weather flight seasons in which the butterflies were relatively numerous, I've found Emperor larvae at the rate of one every 15-20 minutes. That's the rate I expected when I started this season's autumn searches...
And I'm not finding signs of failed larvae either (e.g. unhatched eggs, egg case bases with no sign of larvae, and vacant seat & feed leaves +/- the old egg case base where larvae have been predated). Normally, I find a fair few of these failed breeding attempts (which I dutifully record).
It may well be that unhatched eggs are no longer around, having come unstuck in the heat (as suggested by the shortage of egg case bases where I do find larvae). Note that there is a known issue with eggs not hatching in heatwaves and Nick & Sam Brownley recorded a number of eggs failing to hatch in Sherwood Forest earlier. I have not recorded eggs coming unstuck before.
Moreover, I'm finding very little else - and I also record moth and sawfly larvae whilst searching the autumn sallows. So, hardly any Pebble Prominent and Clouded Border larvae (just one of each), and no Buff Tips or larvae of the sallow sawflies. Worse, I'm finding no signs of Pebble Prominent larvae beyond, say, about 1/3rd grown - their larval feeding damage is diagnostic, this:-
I am strongly suspecting a catastrophic event, or at least something severe... but whatever has happened is outside my experience.
Caveat: My autumn searches are done from the ground. I haven't been able to climb sallows for several years due to severe osteoarthritis in both knees (I await at least one replacement kneecap). Crucially then, my writings are based on the assumption that (roughly) the same % of eggs is laid low down each year - and there's no data to suggest that this is the case, or isn't...
Much depends on the Dangle Leaf season at leaf fall time (the easiest way to find Emperor larvae in most autumns).
Watch this space...
