Thanks are due to Derek, for uploading the map. Good to know that a word document cannot be uploaded to this blog: it has to be converted to a jpg file.
The map shows Derbyshire [no sightings yet], Nottinghamshire [not many habitats yet, but spread across the whole county], and Leicestershire [a number of sightings, most concentrated within the National Forest area in the north-west of the county.
Since moving to Sheffield from Buckinghamshire, I have become increasingly interested in the appearance of HIM in all areas to the north of Rockingham Forest [Fermyn Woods]. I am grateful to my new friends from the East Midlands branch who have generously supplied me with data, in particular, Richard Jeffery, Ken Orpe, Suzanne Halfacre, and Jane Broomhead. Ken Orpe kindly generated this distribution map.
Leicestershire has been particularly fruitful; in particular, the National Forest region has been very good for recorders with several new habitats having been registered. Nottinghamshire less so, but it is particularly exciting to announce sightings, one adult and four larvae [two close together on one bush Matthew!], in Sherwood Forest. Matthew notes in his book that it was last recorded there in 1939. Congratulations to Samantha and Nicholas Brownley, who made these observations, with supporting photos. With Chambers Farm Wood in Lincs, this is the most northerly known habitat. Of course, we cannot rule out releases being responsible for these sightings.
Nothing in Derbyshire yet, but they are getting ever closer to the border. Ken Orpe will open a bottle of champagne when it happens!
I have not included Lincolnshire. HIM is well established in several woods south of Grantham, and in Chambers farm wood in the north of the county.
For the last twelve years I've monitored the Emperor's performance in Savernake Forest, Wiltshire, by standardised searches for larvae during the late summer / early autumn period, from the ground. The data are shown in a table on Page 236 of His Imperial Majesty, a natural history....
This is what I look for -
The 2020 tally is a mere nine. This is by far the lowest total in the 12 years. The previous lowest annual total was 16, in 2019. The mean for the previous 11 years is 55 (the running mean is now 51).
This meagre total is entirely due to a very poor egg lay, as the adults got blasted away by gales in late June and early July - before they'd laid many eggs.
The quality and quantity of the sallow resource in Savernake is actually quite high at present (though sallows close to Grand Avenue remain largely unsuitable as in dry weather their foliage gets covered in dust generated by speeding vehicles - Range Rovers and SUVs mainly; see Book, pages 236-237). There haven't been any problems with sallows droughting off in Savernake (though there have been in Sussex).
Ben Greenaway is finding a similar paucity of larvae in Southwater Woods in West Sussex, though he hasn't finished searching yet.
This means that the prospects for the 2021 Purple Emperor season are, at this stage, distinctly poor. But much depends on the winter, when larval losses can be high. The last thing we need is another mild wet winter (when mortality is very high).
Larvae are so scarce this autumn that I've had to abandon plans to search for Purple Emperor larvae in places where the insect hasn't been recorded for ages if at all, like the Forest of Dean, some woods in Herefordshire and into Monmouthshire, and Devon. I'm only prepared to launch a major autumn larval survey campaign in terra nova after a decent egg lay.
Ben and I hope to have large enough samples of hibernating larvae to monitor winter survival rates, so we can compare survival / mortality rates between Savernake and Sussex.
I'll end with an image of hope. I found two larvae on the same spray on an isolated tree in Savernake which has revealed larvae in eight of the last 12 years. It is very rare to find two close by.
These guys deeply resent each other's presence: one will periodically invade the other's seat leaf, where they will lock horns and try to wrestle each other off. Ridiculous, but that's Emperors all over.
This should be a tale of great and greater glory, but is sadly a tale of great woe, with a nasty sting in its tale. More woe is to come.
We were expecting His Gloriousness to emerge in fantastic numbers, as post-hibernation larvae had enjoyed fantastic feeding-up weather, from late March through to early June. But therein lies the problem, there weren't that many larvae.
Each winter I follow a number of wild larvae through, in order to measure winter survival / predation rate. However, this winter I didn't manage to get a measurement - the Forestry Commission inadvertently trashed my breeding area (I can't be critical: they left most of the sallows, it's just unfortunate that those bearing my monitored larvae got felled...). The winter was mild and horribly wet, and such winters are fairly disastrous for hibernating larvae, with predation rates as high as 85%.
Ben Greenaway, who was following a large sample of wild larvae in West Sussex, recorded a predation rate of about 80%. Had I known that (we thought the rate was more like 40-50%) I would not have predicted an annus mirabilis.
In early June, the Emperor then got stuck in the departure lounge, as the weather deteriorated as the bulk of the brood was pupating. That may have done some minor damage.
The first Knepp Emperors were seen on June 13th. My first sighting was a rubbish sighting, which was deeply ominous as great Emperor years kick off in spectacular fashion. Numbers failed to build well.
We had a short heatwave around Midsummer Day, wherein the Emperor flourished modestly. Then the wheelnuts came off, followed by the wheels.
His Gloriousity is vain enough to roost in treetop sprays, and ignores the weather forecast. If He was to roost on the sheltered side of trunks and branches He would have survived the late June and early July gales quite well. As it was, He got shredded, and the equally dim-witted females. A number of crippled Emperors were found on the ground. This one at Knepp -
2017 = 117
2018 = 201
2019 = 101The net result was a very poor egg lay - seemingly everywhere.
That in itself is not the end of the world, for low levels of larvae tend to lead to low winter predation rates - the tits don't find the hibernating larvae, and the insect recovers.
But Knepp got hit by a double-whammy: the poor egg lay was followed by a horrific drought, during the early August heatwave. The bulk of Knepp's sallows are on former arable fields, they're growing densely together on damaged soils - not on the woodland soils they're designed for. They are drought prone. They wilted badly in 2018, when no rain fell between May 31st and the end of July. But that was after a massive egg lay, so we got away with it.
This year's Knepp sallow drought is an order of magnitude more severe than that of 2018, and occurred after a rotten egg lay.
No way is the Emperor going to abound at Knepp in 2021.
This is what many of Knepp's breeding sallows were looking like on August 13th -
In all, I think this was the worst Purple Emperor year since 1990, when a mild, wet and stormy winter gave way to a magnificent early spring and May, only for the weather to collapse in early June - probably as the first adults were emerging - Only, in 1990 heatwave conditions returned in mid-July, too late for the adults, and persisted.
Pray very hard... We need a wet autumn, a bitterly cold and frosty December to de-tit the woods, a cold winter, a steady non-early spring, a fine May, and a decent June and July.
The last of the 2020 Knepp Purple Emperors was seen on July 23rd. Elsewhere, sporadic sightings were made into early August, mainly in the north of the Empire, with the final sighting coming from near East Midlands Airport in newly-Purpled Leicestershire on Aug 18th (a female).
The butterfly seems to have done appalling badly at all sites, with the notable exception of Abbots Wood Inclosure in Alice Holt Forest (I'm not sure why, it may be due to an upsurge in recording). In one top grade site, a privately owned wood known as 'Bucks Best Wood', only a single sighting was made.
The message to 2020 is simple: Don't come back!
Female Purple Emperor seen egg-laying in a Sallow today (Monday 10th August 2020) in Minting Wood, part of the Chambers Farm Wood Complex, Lincolnshire. I also saw a female Purple Emperor in almost the same location on Saturday (8th August 2020), so good news for the future generation!
