Spring of 2026

Purple Emperor larvae are continuing to develop ahead of any accepted norms... 

They got held up a bit by a cool and showery week in mid-April, but are set to romp ahead this week, under a strong anticyclone.

Over the weekend of April 18th-19th, 49 larvae were checked in Savernake Forest. Of these, two had recently changed to the 4th instar (L4), but the majority were changing skin. That's early, but not unprecedentedly so. 

Crucially, the sallow foliage is shooting ahead, and caterpillars tend to be in sync with their foliage (White-letter Hairstreak larvae are developing apace).

PE Larvae can race through the 4th instar, in fair weather, though they then take much longer in the 5th and final instar - and they can get stuck at red traffic lights (or a full motorway closure) at any stage, in wet weather. 

Here's an Early L4 larva -

Here's an L3 larva about to shed the skin its worn since last September, and has wintered in. Note the hunched position - 

In late April, Purple Emperor larval feeding 'damage' is fairly distinctive. They feed only at leaf edges, and do not make holes (that's moth feeding). The only thing you can confuse PE feeding with at this time of year is the feeding of the common Willow Nematine sawfly Euura viduata -

The 'record' for the earliest wild 5th instar PE larvae is May 1st (2011). That record is under serious threat this year. 

I repeat that PE larvae have come through the winter remarkably well, and that 2026 has the makings of an astoundingly good Purple Emperor year - unless the weather misbehaves.

Also, again and yet again, this butterfly could be on the wing exceptionally early this year.

Watch this space...  We are living through very exciting times...

     

Spring of 1976...

Fifty years ago, the great butterfly season of 1976 was brewing. I was there, big time: having had the previous eight summers wrecked by the examination system*, I took a self-funded sabbatical, and butterflyed on over a hundred days between mid-April and early September – playing cricket on most of the others. This was low budget stuff, my main form of transport was a three-speed bicycle – and the tarmac melted. I was living near Selborne in East Hampshire, a top butterfly hotspot, but thought nothing of cycling to Chiddingfold Forest. Crucially, I kept detailed diaries.

The previous summer had been hot and dry, and 1974 had been reasonable too. Butterfly populations were on a high. Truly great butterfly summers are the second or, better, third in a sequence of hot summers. ’76 was the third. Incidentally, we have not had a hot summer sequence this century...

The 1976 butterfly season did not begin unduly early, like modern seasons. Here’s some first and last dates, from the Selborne & Alice Holt Forest district:-

Orange Tip                     April 16^th        June 12^th

Speckled Wood              April 19^th            -

Green-veined White       April 20^th       June 18^th

Dingy Skipper                 May 6^th         June 22^nd

Duke of Burgundy          May 7^th          June 10^th

Pearl-bordered Frit         May 6^th          June 6^th  

Small Pearl-bordered      May 23^rd       June 24^th

 

Those are typical start and end dates for central southern England from that era. Butterflies, that summer, didn’t start emerging early until the start of June. Then, Large Skipper commenced on June 1^st and Meadow Brown on the 2^nd (my earliest Meadow Brown of the 20^th century).

The Holly Blue was staging one of its periodic revivals, having been scarce since 1970. The Pearl-bordered Fritillary had an astounding year, with colonies in most young conifer plantations (there were at least ten colonies in Alice Holt Forest that summer, and the butterfly truly abounded in Chiddingfold Forest). 

But Butterfly of the Spring / early Summer 1976 was the Wall Brown, which was almost omni-present – not just on the downs and grassy heaths, but in open woodland rides, along road verges and on garden banks. My diaries record some 250 Wall Browns, between May 10^th and June 18^th, but I didn’t diarise roadside and garden sightings. I saw over 50 in Lodge Inclosure of Alice Holt Forest on May 23^rd. This abundance occurred after a massive 3^rd brood during the sublime autumn of 1975, blowing a hole in the theory that a 3^rd brood depletes populations and is responsible for the current decline. Common Blue and Small Copper were comparably numerous.

The spring weather wasn’t too extreme. April was dry and merely pleasant, and May started and ended rather poorly, though it included a couple of strong anticyclones. The heat and the drought were to come later. This meant that spring butterflies were not unduly stressed, laid a lot of eggs, and had lengthy flight seasons. It was also a great time for larval development. All the while, the Purple Emperor season was brewing...

Next Time: June & July '76.

*Rant: why oh why didn’t we reset the academic year during the Covid pandemic, so that exams take place in the autumn, and we allow our young folk to experience spring and early summer? Rant over.

Ministerial Statement

Here is a Ministerial Statement on the State of the Nation's Caterpillars (Rhopalocera):-

'Led, as ever, by His Imperial Majesty, the Emperor of the Woods,  the High Spirit of the Midsummer Trees, The One of Whom the Nightingale Sings - to cite a few of His numerous epithets - the larvae of some of our butterflies are unusually advanced.'

'Purple Emperor larvae had commenced feeding in Savernake Forest, Wilts, by March 18th, equalling or narrowly beating the record set in 2019 and 2020.' 

'Moreover, the sallow foliage is now unprecedently advanced, following a mild winter (our last cold spell was at the start of January) and the mid-March anticyclone.  Sallow blossom is currently at peak.'   

'Also in the woods, some White Admiral larvae are already feeding, some Pearl-bordered Fritillary larvae have reached their final instar, and if you want something utterly barking, look at the advanced state of White-letter Hairstreak larvae - they're likely to be on the wing in early May.'

'At this range, unless the weather deteriorates, the Purple Emperor is likely to be out by early June, breaking the long-established record set in 1893. Numbers could be astoundingly high, as larvae have come through the winter well.'  

Some Emperor larvae have been feeding by 'bud biting', like this (Savernake 18th March 2026):- 

Most, though, are lined up alongside sallow buds, waiting for leaf buds to loosen, or sepals to darken and open, so they can commence feeding. They are well greened up, like this:-

Watch this space, and get very worked up...

 

The New £20 Note...

We are pleased to announce the new Royal Mint £20 note, with an Emperor as Monarch...

Meanwhile, Purple Emperor larvae are getting ready to start feeding. Many are greening up next to flower or leaf buds. Their first meals will be on loosening buds, by 'bud-biting', or on darkening sepals (they wont feed on very pale, 'anaemic' sepals). 

In general, Emperor larvae are decidedly advanced - as is the spring of 2026. It is quite possible that a few larvae have already had their first post-hibernation meals in the warm South East.  

That's remarkable, as it was only a couple of years ago that the first-ever March meals were detected, at the very end of the month. Now we're heading for a mid-March feeding start. 

We may be heading for a Very Early Flight Season... Watch this space.

On The Move!

The current mild spell hasn't just woken hibernating butterflies, like the Brimstone and Red Admiral, but Emperor caterpillars.

Emperor catties are now waking on mass, and are relocating themselves to align alongside swelling sallow buds. A surprising number of them have hibernated in forks and on twig scars this winter, some distance from the buds. We don't know why. 

It is, of course, unusual for them to waken this early, and they're going to get stuck in the caterpillar equivalent of the dreaded airport Departures lounge for ages, waiting for the sallow leaf buds to start to open.

This is a hazardous time for them, as they can be picked off by predators, birds especially, when moving. Here's one moving up-stem, yesterday, a journey of at least 2m (he's just above the upper fork) -

Also, many are greening up, early, like this one below - 

Watch this space...

 

The 1970s

Here are the known start and end dates for Emperor seasons between 1975 - 1980 in and around Alice Holt Forest, East Hampshire. This is quite accurate data.

Year        First Sighting        Last Sighting        

1975        5th July                   2nd Aug        

1976        25th June                17th July                 

1977        23rd July                11th Aug                 

1978        15th July                13th Aug

1979        17th July                18th Aug                  

1980        20th July                25th Aug                  

What's interesting - beside the obvious fact that most of those seasons didn't start before mid-July - is how short most were.  

This is because most seasons were curtailed by either extreme heat (1976) or by adverse weather events (in 1977, the adults were knocked out by very cold nights at the start of August; in 1978, they were knocked out by a returning Polar Maritime depression). 

Times have changed...

 

 

Fingers Crossed...

 

Emperor larvae seem to be surviving their five month long winter hibernation period relatively well. 

Over the weekend, three of us checked 56 hibernating larvae in Savernake Forest, finding 47. Losing just nine out of 56 during the January and early February period isn't too bad - in fact, it's almost as good as it gets...

At this stage, it looks as though winter predation is only going to be in the Modest bracket, and not High. However, February and early March is the main period for losses. So, fingers crossed...

Some larvae, like the one above, are starting to green up. Now, that's early, very early, but this has so far been a very mild winter. Also, two had moved, up to buds.

If (underlined and italicised) winter losses remain in the Modest bracket and if (ditto) the weather is fine during the crucial pupation and pupal periods, 2026 could (ditto) see a sizeable Purple Emperor emergence - the two key stage periods of loss which seem to determine adult numbers are 1) winter and 2) pupation / pupal time (+ flight season weather, of course).  

Watch this space. We're not there yet, but we seem to be heading there... 

All things are for the best with this the best of all possible butterflies.