Dangle Leaf Time...

Purple Emperor larvae have been disappointingly scarce this autumn. My annual autumn tally in Savernake Forest, Wiltshire, determined by standardised searches, was a meagre 22 - less than half what I'd expected.  

It now looks that the July weather was too poor for the laying females, and that the egg lay was consequently low - at least away from the East Hampshire, Surrey and West Sussex region where the butterfly enjoyed an annus mirabilis.  

I have yet to find any sign of the insect in my local patch, Cirencester Park Woods, Gloucestershire - in over 50 hours of searching for larvae. This is in part due to the severe outbreak of Melampsora Willow Rust mentioned in my previous post, which has been rampant in the Cirencester / Cotswold Water Park area, but also in part due to poor flight season weather reducing the egg lay in what is a very small population, of recent origin.  

Everything now depends on the Dangle Leaf season. Dangle Leaf is a method for finding PE larvae as autumn merges into winter. 

In brief, during early to mid- autumn, larvae assiduously silk their feeding leaf stems on to branches, before wandering off to find somewhere to hibernate. The petiole join then breaks, only for the leaves to remain attached for a while by silk, dangling or even spinning madly. These dangles are diagnostic of iris, no other insect does this. 

In wet and winter autumns the dangles quickly fall off, especially on larger leaved sallows and along windward edges. Dangle Leaf is therefore about as reliable as Floo Powder in Harry Potter or the Rhythm Method in family planning - but it is quick, picks up larvae just above normal ground-searching level, and can be hugely effective.  

This is Dangle Leaf - 

Those two leaves are attached by silk strands, the hibernating caterpillar is directly above (though most larvae wander further away, and can be found as far off as 3m from their abandoned feeding station).  

The 2023 Dangle Leaf season is running a little late, as most sallow bushes have remained green in the absence of frost (this is a very mild, if horribly wet autumn). But it is kicking off now. 

Weather permitting, the Dangle Leaf season should last from mid-November to the start of December, possibly beyond.

Give it a go, it's insane...

Egg Lay & Willow Rust: Important News

I'd anticipated that autumn larvae would be fairly numerous this year, but it looks as though I was wrong, again.  Badly. 

Initial searches suggest that the egg lay was low.  Certainly, larvae are hard to find, if not very hard.  It's relatively early days though, as I've been doing other things, but the signs are ominous.

It now seems that the females hadn't got into the swing of laying before the weather deteriorated in early July and, critically, that many of them were blasted away by the St Swithun's Day gale - before they'd laid many eggs...

Worse, far worse: the broader-leaved sallows in some districts have been severely affected by Melampsora Willow Rust.  I've been aware of this rust since 1977 but it's never been too much of a problem, swelling up in wet midsummers, but abating before autumn.  

This year, it's rendered most of the broader-leaved sallows in my home patch (Cirencester Park Woods) wholly unsuitable: many sallows there had dropped most of their leaves before the end of August, others were covered in golden leaves that are destined to drop early.  I haven't found a single larva of any Lepidopteron or sawfly species on infected sallows.  Here's what to look for:

Early Stage Infection -

Then it gets Serious - 

  Then this happens -

That photo was taken on August 21st!  It shows some resprouting, from a largely senescent sallow.  

Here's a leaf underside close up - 

All the broader-leaved sallows, plus the poplars and aspens in the Cotswold Water Park (another study site) are severely affected, but Savernake Forest and Bentley Wood (both recently visited) seem OK.  The pox seems to start at Junction 15 of the M4 (Swindon East).  

Crucially, narrow-leaved sallows (Salix atrocinerea & S. cinerea types / hybrids) seem far less affected. 

PLEASE LET ME KNOW IF YOU COME ACROSS OUTBREAKS OF WILLOW RUST.  We need to gather evidence (I'm liaising with Forest Research's Tree Health Dept. at Alice Holt Forest).  Email me on matthew@matthew-oates.co.uk  

Final sighting

The last Purple Emperor of 2023 was a female seen in Ruislip Woods on August 3rd. This means that there were only three sightings in August: this one, and my two sightings in Savernake Forest on August 1st. 

Perhaps the key point about the 2023 Purple Emperor season is that it arrived earlier than anyone anticipated and caught us with our trousers down... By the time many observers had realised that the butterfly was in fact well out, the weather was deteriorating. The St Swithun's Day gale effectively ended the season at many sites.

Numbers were excellent, if not superb, in central southern England - even in places where sallows were severely affected by drought in July and August 2022, and shed many leaves. This suggests that the Emperor may be becoming drought proof, like the White Admiral.

Elsewhere, numbers were at best modest - but many recorders got out rather too late in the flight season, and the butterfly may have been under-recorded.

Here's the pupal case of a female, who hatched out circa June 30th, in Cirencester Park Woods, Glos, taken on August 14th. The cases can persist for weeks, or months. 

The long journey into the 2024 Purple Emperor season has started. I'm beginning to look for larvae. Watch this space...

Tues August 1st: The End...

Just two octogenarian males left in Savernake, on their final hours. They'd all but run out of fight. One was so tired he failed to rise to a Honey Buzzard flying just over the treetops. Here he is - 

The journey towards the 2024 Purple Emperor season has already begun... The end is where we start, to reach an end is to make a beginning...

Sat July 29th: Still Going...

I returned to Savernake today, and managed to see 8 more males. It was sunnier but much windier, which meant that territories on higher ground were scarcely occupied. I found two new territories on lower ground, one which held two sparring males. 

This might be my last Emperor of 2023 -

'In my end is my beginning...'

They are still going at Knepp, just. 4 were seen there yesterday, after a gap of several days.

 

Fri July 28th: Still Partying in Savernake...

A cloud-spoiled afternoon along Three Oak Hills Drive in Savernake Forest gave sightings of 9-10 males in four known territories. All bar one were torn and worn. 

Ten minutes of sun at The Dead Beech Glade produced a squabble of three males, and I also saw three in a vista at another territory further on from The Column.

Incredibly, two perched 1m apart. Here's the pic, taken from some distance below (Sav's Beeches are 90-120' tall). Spot the Emperors -

And here's a lone male perching - 

As usual, none was seen in The Column glade, which is only a secondary territory. Yes, that's where everyone goes to see iris in Savernake, and they occasionally do quite well there, but they walk past the best primary territory - the Dead Beech Glade at W3W gold.subtitle.applies - 

Depending on the weather, there's a few days left in Savernake...  

PE seems to be over now at Knepp - no sightings there since Tuesday 25th.

Mon July 24th: Final Sightings...

The Emperor season was hit by another bout of rain on Sat 22nd. I managed to see an OAP male over one of the favoured feeder tree oaks at Knepp an hour before the rain began. Red Admirals were feeding on the sap bleeds there. 

The Red Ad is, of course, staging a mighty bold bid to win Butterfly of the Year - and with a homegrown autumn brood to come...

Oddly, I spotted a male Brown Hairstreak perched on one of the favoured male perching sprays as steady rain arrived.

Since then, there have been single sightings at Knepp on Sun 23rd and Mon 24th, a sighting of a female in Bernwood Forest on Sun 23rd, and sightings on Billa Barra Hill in Leicestershire on Sun 23rd and Mon 24th.  

The race is on for the last iris of the Great 2023 Season (which wasn't great in East of England region, but was just about everywhere else, and was stupendous in Central Southern England). 

This Blog, of course, carries on all year round, covering adventures with the immature stages...

An unusually large number of eggs should have been laid this season, and larvae should be relatively numerous this late summer and autumn. Therefore, this is the year in which to look for new populations by searching for the immature stages. Herefordshire, here I come... ... ...