Early Hibernation?

This 'pillar yesterday, Sat October 19th, was fully coloured up (complete with bronze V) and in pre-hibernation pose - about to quit the leaf for bud or stem (unless it had decided to hibernate on that terminal leaf).

Crucially, it had little choice as its sallow tree was 99% bare due to the ravages of Melampsora Willow Rust. How it had fed up to a decent hibernation size on such a depleted tree only the Good Lord knows...

Here's it's tree - 

For the record, the earliest dates I've recorded larvae in hibernation are 17/10/2010, 21/10/2016 and 23/10/2009 - all on early leaf-fall sallows.

 

Knepp 2024

Here's the data from the Purple Emperor transect at Knepp, which runs for 2km down an oak-lined green lane bordered by sallow thickets. It's a single species transect (ignoring all other species), which is walked once a week during the PE season, in afternoons only (from about 12.20), in decent weather (wind is a problem at Knepp), when males are on territory and, crucially, has a massive recording box, and takes about 3 hours:-  

 

This is good data. The UKBMS data is restricted to the standard 5m recording box and largely records males feeding on dog poo. 

The Knepp data suggests that PE had an 'average' year in 2025. However, counts during Week 1 and Week 2 were relatively high. Indeed, the 2024 Week 2 tally was the second highest for that week in the whole data set, only bettered by Week 2 of the 2018 annus mirabilis. 

What happened in 2024 is that the butterfly got systematically blasted away by spells of foul and abusive weather after Week 2. The Week 3 count was way below what it should have been. This is largely because the numpties insist in roosting in sprays in the oak tops, rather than on the leeward side of limbs... Had the weather not broken the annual total would have been in the region of 150-160.

Below are the PE season start and end dates at Knepp. Again, this is seriously good data, derived from diligent recording. This site is very well monitored.

First & Last Sightings at Knepp  2014 - 2024

        (earliest & latest dates in bold)

        2014    18th June     31st July

        2015    30th June     >21st July

        2016    27th June    3rd Aug

        2017    15th June    25th July

        2018    17th June    26th July

        2019    25th July    31st July

        2020    13th June  23rd July

        2021    2nd July     19th Aug

        2022    16th June    29th July

        2023    20th June    25th July

        2024    17th June    1st Aug

Just note how early PE starts there in this modern era, and ignore what the books say. Sooner rather than later a May iris will be recorded at Knepp...  

Only 2021 was a traditional year, with old-fashioned start and end dates.

Also note that PE has only been recorded in August during three of the 11 years.

Purple Emperor pages are being updated on the Knepp websites. 

  

 

  

 

Mid-October Doings

Purple Emperor larvae continue to be unusually scarce just about everywhere this autumn. All bar one recorder (Ben Greenaway) is struggling to find any.

Savernake is going to record its poorest autumn larval count in 16 years of diligent, standardised effort. This is primarily due to:- 

1  A shortage of the younger sallow growth that the females favour (i.e. trees or young branches off mature trees which are just becoming mature enough to flower). This is a problem currently peculiar to Savernake, which is experiencing a lack of sallow regeneration (in part due to squirrel damage - bark stripping, in part due to a break in continuity of ride widening).

2  Coarse foliage, caused by sallows coming into leaf early this year, after a mild winter. First instar larva can't cope with thick leaves. This is a problem everywhere this year.

3  The ravages of rampant Willow Rust, which has rendered many broad-leaved sallows seemingly unsuitable (+ Tar Spot). This is even worse around Swindon and Cirencester, but all but absent in S Warwicks & S Worcs.

4  But, clearly, the 'egg lay' was very low, at least low down.  

However, there is a scatter of larvae around. I was amazed to be shown one on a young sallow rendered 95% bare by the ravages of Melampsora Willow Rust - the small tree on the left, with my gold shepherd's crook. The finder, co-worker Gary Tucker, is looking at the bigger tree - 

That 'pillar is starting to colour up - 

It's not just Emperor larvae that are scarce on the sallows this autumn. Other sallow invertebrates are perhaps even scarcer: I'm scarcely finding any moth larvae, though some moth species may have finished for the season; Sallow Flea Beetles are decidedly rare; I haven't found a single sallow sawfly larva all autumn; the normally common cabbage-like galls of the midge Rabdophaga rosaria are rare, and even the tiny galls that normally abound on narrow-leaved sallows are generally absent; and I've hardly found any Dicranopalpus harvestmen spiders... In fact, the Purple Emperor is actually faring relatively well!!!

Fingers crossed that yet again this the best of all possible butterflies will show itself capable of out-manoeuvring all the nonsenses that gets thrown at it... 

 

Sallow Foliage Conditions...

Purple Emperor larvae remain seriously scarce this autumn: on Saturday, three of us found two larvae in some 15 hours of foliage searching in Savernake. One larva had only just changed into the 3rd instar - its old head was lying close by; that's late.  

Tony Kasiske reports a similar scarcity in Germany, again due mainly to poor flight season weather.  

Interesting to find a sizeable and healthy-looking larva on a branch heavily infected by Melampsora Willow Rust, note the feeding marks -

Most of Savernake's sallows are in poor condition for larvae, with Willow Rust, Sallow Mildew and Tar Spot. Worse, everywhere, sallows came into leaf unusually early, following the mild winter; this means that the leaves were unsuitably thick and coarse by the time first instar larvae were feeding. It may be that a lot of L1 larvae failed, but we wont know as most egg case bases got washed out by heavy rains. 

One again, iris has got to outmanoeuvre a lot of problems if it is to fly in numbers next summer; but don't underestimate him - for a start, it's likely that tit predation of hibernating larvae will be relatively low this coming winter.  

Here's what one of my favourite sallows in Savernake looked like on Saturday, with white mildew on a lower bough, sparse and thick-leaved foliage and a lot of Willow Rust (plus squirrel damage, back right).  We didn't find anything on it -

And here's what a healthy, suitable sallow should look like in Sept - 

complete with damsel not in distress...

 

Early Autumn Larvae: Not Good News...

My first post for a while... (I've been hors de combat). 

Incredibly, it seems that I topped and tailed the 2024 flight season: I know of no adult records subsequent to mine on Aug 11th, nationally...  

It looks as though larvae are in low or very low numbers this early autumn, though I'm only just getting into the swing of looking for them. I've had a big session in Savernake, and have looked in Cirencester Park Woods and at Lambourn (the latter two sites only support very small populations).  

Bad news: None so far at Cirencester and Lambourn, and a big session yesterday in Savernake (3 searchers, totalling 14 hours of actual foliage searching) produced only one mid-2nd instar larva and a 1st instar fail + egg case base. Here's the one we found, showing distinctive feeding marks on a classic midgreen soft matt leaf - 

One major breeding area in Sav drew a total blank, suggesting that Herself hadn't wandered there. 

The main problem at all three of my study sites is finding suitable foliage: sallows in exposed or open situations are heavily infested by Melampsora Willow Rust, and / or are too thick-leaved (because the sallows came into leaf ridiculously early), and many overhung sallows are heavily coated in Sallow Mildew (which proliferates in wet autumns). 

Sallow foliage quality is, fortunately, quite high in shady situations. So there is Hope... 

Here's a Tree Damsel Bug Himacerus apterus, found on sallow in Sav yesterday. This is a serial killer of caterpillars and persona non grata on sallows (I translocated it onto a birch tree, and told it to Go and Sin No More)... 

   

Sun Aug 11th: Last Post in Savernake

Checked the best territories in south Savernake today. Just this one male, in reasonable condition, in the Dead Beech Glade for 40 mins either side of 3 O'clock. Then, realising he was all alone at the party, with not even a bumblebee to chase, he drifted off and away... 

Sat Aug 10th -Still Flying in Glos!!!

The most worn and faded Emperor I've ever seen was smashing things up this afternoon at Sapperton, W of Cirencester, Glos - a faded pinky-yellow in colour, rather like a very worn migrant Painted Lady. The wind prevented me from photographing him.  At one point he eviscerated a high-flying Large White.