July 8th: Heatwave Intensifying...

Today brought very difficult weather conditions in which to work Emperors, especially late in the flight season: cloudless, calm and hot from early.

In such conditions, late on in the season, Emperors tend to stick to the vicinity of their feeder trees, which are usually sap bleeds. Sap runs are never easy to find, and can switch on and off from day to day. This year, they have been even scarcer than usual - Patrick's Tree, normally Knepp's No 1 feeder tree, has hardly functioned...

I was in a new part of Savernake today, and quickly learnt that weather conditions weren't right for surveying. The one sap run there, the best I've seen anywhere this year, attracted half a dozen male Red Ads, and briefly this old male Emperor (and it is male, it's completely lost its purple iridescence) -

The signs of an ageing season were everywhere, including this pupal case remnant, from two weeks ago -

and the next generation of larvae is advancing. Here's a late 1st instar larva, soon to change to the 2nd instar, and gain its horns - this early, rather begging the question of whether we'll see some 2nd brood Emperors on the wing this autumn???

Elsewhere, it looks as though the Purple Emperor is over in Alice Holt Forest, Hants, already...

  

Tues July 7th: Going Over?

Time was when the Purple Emperor season would normally start on or around July 7th. This year, the butterfly is now past peak and probably starting to go over at early sites in the south east. The length of the tail will be determined by the intensity of the current heatwave.

The woodland vegetation provides a better indication of real time than our calendar. Look at the oaks, and the sallows, and everything else. It's late July out there...

It appears that 2026 is at best a rather modest year for the Purple Enperor, numbers-wise - but populations have been hard to monitor due to extreme heat and unforecast winds, generating a pattern of days of relative activity punctuated by days of extreme lethargy. 

Yesterday, I visited the central Malverns, straddling the Herefordshire - Worcestershire border, where Emperor males were discovered genuinely hilltopping last year, and were seen again last Wed and Thurs. 

These are the first records I know of Emperors hilltopping in open terrain in this country, though odd individuals have been seen on the crest of the South Downs (seemingly wandering over, rather than setting up and defending territory). 

It was too windy yesterday, with a Fresh westerly blowing on the Malvern tops. We saw a nice scatter of old sallows with suitable-looking foliage on the western (Herefords) slopes. Here's the habitat, where males have been perching on bracken tops - 

Elsewhere, Emperors have been seen in three sites in Yorkshire (but none in Lancashire), some new places in Derbyshire, and has been rediscovered in Devon. 

 

Fri July 3rd: an 'average' year...

Walked the Knepp Purple Emperor transect this afternoon, for Week 4. Counted 32.

That makes 2026 an average year for the PE here, even if they burn out fast in the coming heatwave (which they may well do).  

They have been very hit and miss here this year - localised and episodic.

Today was my last day at Knepp.  Off home early tomorrow, to work Savernake and elsewhere...

Here's my signing off photo from Knepp - 

 

 

Thurs July 2nd: Hungover...

Struggled to see Emperors at Knepp today. It was too windy, yet again, but the two sap run trees which had been heavily favoured these last few days both drew blank, and most of the favoured male territories were empty too. Sap runs can suddenly switch off.

Conclusion: both sexes got so plastered during the football last night that they took the day off, hungover. I can't think of any other explanation...

The best I managed from today was this photo of a female sapping next to a Red Ad on the feeder tree next to the tree platform down Green Lane - 

Tomorrow's my last day here. Need to finish on an almighty high...

   

The Purple Emperor Rescues England

Watched the first half of England v DRC. Decided the cause was lost, so went out Emperoring on bike, listening to the match on the radio.

Both England's goals were set up by the Purple Emperor butterfly. Both goals resulted from magnificent 'tumbledowns' (mated female rejecting a wont-take-no-for-an-answer male). Here's Kane's winning goal -

Interestingly, there are still a fair number of fresh-looking males around at Knepp, and males are still 'sallow searching' (for females and female pupae).  

 

Tues June 30th: Apatura iris in cop

Briefly, as I'm too tired. A pair joined at 4.05pm on the shady leeward side of a feeder oak, just 25' up, after meeting in flight. No courtship (he didn't even ask her name...).

They remained together, motionless, wings closed, for a marathon 4 hours and 2 minutes. The average duration prior to this observation was 3 hours 42 mins, from a sample of 19 pairings (now 20). Gentlemen of England, Ladies even, we are outdone, by a butterfly...

We managed to show them off - and a lot more - to one of Knepp's famous Purple Emperor Safaris (estab. 2014) - 

All previous pairings I've seen have been in the tops of tall trees. Really good to see them so low down.  At one point I saw 6 males and 2 females in a vista by that feeder tree.

Onward!

 

 

Mon June 29th: Knepp Transect Data

The Purple Emperor is now at peak at Knepp. 

Today, I walked the Knepp PE transect. This runs down 2km of oak-lined green lane and takes around 2 hrs 30 mins to walk. Weather conditions were Good, with Emperors nicely active (a wind sprung up towards the end - Knepp is a surprisingly windy place).

I totalled 38, including 5 females. 

That's about par, suggesting that the butterfly is in average numbers at Knepp this year (though way down on last year's stupendous showing, which produced a record individual transect count of 80!). 

However, if another extreme heatwave comes over, they'll shoot over early (as happened last year, and in 1976) - in which case this year will become a below average year...

At last, some of Knepp's oaks are producing sap runs. Both males and female cluster around these 'feeder trees', which means they tend to disappear elsewhere. 

Here's some feeder tree action from 2025 -