Benjamin

[bugboy]

I've been taking careful note of your recent posts and trying to use your patented dangle method when I visit Bookham, so far no luck but I shall persevere (could that sentence be used against me if taken out of context? )

[Benjamin]

That’s right Wurzel - the more tickets you get the bigger the piece of plastic crap that the kids get to bring home. If I weren’t so insecure I’d have missed on purpose - damn.

That’s right David - if you want to learn about your subject then it’s always worth going out - they’re always there somewhere after all, and let’s face it - we’ve all seen them flying around in the sun!

Good to know my extremely niche videos are of interest to at least one fellow enthusiast Paul! Plenty to interest you in this exceptionally long-winded post if you’ll be heading out in search of dangles…..

Having missed a week in the field due to kids half term (I can’t even kid myself that they enjoy a day being dragged around the wet woods when summer’s over) I knew that I’d see a jump in progress when I returned to the site this week.

The rain of half term had passed and with the sun out and still providing lovely warm midday temperatures I really did feel blessed to be spending these few days studying my subject in these wonderful autumnal woods. I don’t always feel that way, as I’ve mentioned before (the freezing drizzle that can seem to drag on for half a year will arrive soon no doubt) so I must make sure I acknowledge the good, and these last few days really were good.

The caterpillars I have under observation
have coloured up fast, with the earliest movers now tucked up (I wish I could say ‘safely’) in their winter resting spots. The majority, however, are still sorting out their winter wardrobes and remain firmly attached to their heavily silked-on leaves.

I took a short video showing a caterpillar that had travelled around 3m to its final resting spot. This is just to show the kind of distances they can travel, and to demonstrate that a systematic search starting from the dangling leaf and gradually working further back into the tree is really the only way of concluding with a good degree of confidence whether or not a missing caterpillar has been predated. Naturally I search each and every branch/twig that splits off from the main growth before moving further in.

https://youtu.be/rvcV9pSdJWk

As they enter hibernation I’ll give them names. I’ve decided to keep the grandmasters for another year, and am returning to my comfort zone - sport. Great British Olympians will be the theme for this year, and after one of the longest journeys into hibernation that I’ve recorded so far, I’d better start off with Magic Mo Farah.

A little distance down the ride I found another such journey in progress. Another short video included here.

https://youtu.be/aaHAU589yac

I monitored progress for about an hour, hoping to see the final selection being made, but with no decision in sight I left him to it and continued on elsewhere. Returning a couple of hours later he was still going over ground that he must have investigated several times already. He certainly appeared to be searching most diligently for the very best place to see out the winter months. Returning the following day, however, I found him finally settled no more than 10cm from his vacated final leaf! He must have walked well in excess of 5m just to return to where he started. It was a lovely afternoon for a walk I guess, and with the next 5 months of inactivity looming large, who can blame him? I’m not sure why but this seems like the kind of thing that Seb Coe might do, so welcome to the stable Sebastian.

Red admirals were the only butterflies putting in an appearance - presumably having missed the last boat south, or having made what I would consider to be the very sensible decision to stay put, drink alcohol and enjoy the occasional cruise around the now calm and deserted sunny rides. Peace and quiet and a little something to soften the edges - heaven.

It was a good day for photography. Well, certainly for someone who struggles in the gloom - so a few pics of those that remain on their leaves. Hopefully they’ll all be making the move soon and I can decide on a few more of my favourite GB Olympians.

The only one on caprea so far - doesn’t he look lost on those giant leaves!

Dangling leaves are starting to appear, so I’m finding new caterpillars on every trip. There are, however, a lot of leaves still on the trees, and the best dangles (final feeding/resting leaf) are largely still to fall, so although underway, my search is yet to reach top gear.

Early signs regarding numbers are positive, but it’ll be closer to xmas before I draw any firmer conclusions. I hope to be out in the field 2 or 3 days a week for the next 8 weeks or so - I should think again about the coat situation.

[trevor]

Sterling effort again, Ben. As the rest of us hang our cameras up for the Winter,
your ' season ' is just starting. Let's hope the wetter Summer this year kept the
Sallows in good condition, unlike the previous two years when the trees suffered
in the dry conditions and nutrition for the new cats. must have been poor at best.
Hopefully there won't be large scale predation of larvae this Winter, and 2022
will be an epic Emperor year!. We are owed one.

Great work, stay well.
Trevor.

[bugboy]

I might have found myself a dangler today . Had I remembered to bring my glasses I might have stood a chance at locating any larvae so will have to look again next time I'm here.

[Wurzel]

Sterling work Ben and those autumnal shots do make it look like a brilliant setting I'm with Trevor, hopefully the winter and spring will be kind and we'll have a bumper Emperor season in 2022

Have a goodun and stay safe

Wurzel

[David M]

...I took a short video showing a caterpillar that had travelled around 3m to its final resting spot. This is just to show the kind of distances they can travel, and to demonstrate that a systematic search starting from the dangling leaf and gradually working further back into the tree is really the only way of concluding with a good degree of confidence whether or not a missing caterpillar has been predated. Naturally I search each and every branch/twig that splits off from the main growth before moving further in.

Nice film that shows the context of what you describe, Ben. 3 metres may not sound a lot but it must be like 3km for a small larva. Your dedication in finding and following them is admirable and I hope your efforts this autumn and winter will be suitably rewarded with an 'Olympian' return next spring.

Good to see you had company in the form of atalanta!

[Benjamin]

Cheers Trevor - didn’t feel like much of an effort last week I must stress - in the warm sun it felt more like cheating really! It will change……

Fingers crossed Paul, and if you do find one then search nearby! A selected tree should receive half a dozen eggs or so from a single undisturbed female. Of course many will be predated as eggs or in the early instars, but it’s quite rare that I only find a single individual in hibernation - usually if one has survived, then 2 or 3 more can be found within 5 metres or so (same tree or nearby).

Thanks Wurzel. I had hoped that we’d rebuild this year, have another decent egg lay and then boom in 2023, but as so many factors come into play each year I think we’ve every right to be hopeful that next year could be big, and pinning our hopes on anything further ahead is to detach ourselves from any vague notion of understanding and exist in fantasy land. Not that there’s anything wrong with that! I am still hoping 2023 will be big - I just have to accept that if it is, then it’s unlikely to be for the reasons that I’m currently imagining. Know your limitations.

Thanks David - the only reward I need is the experience that comes with time invested. I saw relatively few emperors on the wing last year but it didn’t really matter, it was a very productive year. I wouldn’t say no to a bumper year though, but mainly because I’m really interested to see how the egg lay and caterpillar numbers would look at my site following such a year. With foreign trips opening up I’m also probably not going to be here much during July - I’m hoping for an early one!

Back again on friday to check on an individual a little outside my usual range. He was fairly mid-pack in terms of progression - nicely coloured up, making exploratory journeys, but returning to his heavily silked-on (soon to be a major dangle) leaf.

Clearly the joint receives a lot of attention

With the low afternoon sun catching his silk trail at the right angle, I thought I’d take a few photos to show just how extensive these silk roads are. Presumably the prolegs have tiny hooks that interact with the silk to achieve a firm grip - Velcro like. This is certainly true for lots of species so I guess it’s true here, but if somebody knows otherwise then please set me straight.

I also found a new caterpillar very close to the pupal case of X2 (star of my drone attempt). Empty cases can persist for several years if the leaf is particularly well silked, but this one looks like it might drop this winter. This is really just an excuse to brighten up my diary with another photo of X2 from the summer.

Finally I think I may have been wrong about this one. I thought this leaf would be a dangle any day now, but it looks to be a ‘shriveller’ and as such won’t drop. I’m not sure if the caterpillar knows this and selects it as such, or is just waiting for a cue to depart - a cue that in the case of a ‘shriveller’ won’t come. I guess they can feel the weakening of the joint at the base of the petiole as the tree attempts to shed the leaf, and can therefore vacate in good time. Presumably a leaf that shrivels and doesn’t drop doesn’t go through this process and so possibly the caterpillar just remains where he is. This particular tree produces a lot of ‘shrivellers’ as it struggles more than most with drought in the summer - it has so far hosted a leaf-dweller like this every year.

If he stays for another week I’ll name him…..

[Benjamin]

He’s still there and looks set so he can join Mo and Seb in the named 20. I may actually name a few more this year, but these first 20 will be the set from which I take my overwintering data.

James from above

James from below

Welcome to the stable James Cracknell. Well - it looks a bit like a boat doesn’t it??? I know Sir Steve should really be first choice of the rowers but I’m going with James. I understand he loves a challenge - one of those guys that has to have an almost impossible project in his sights to make life worth living. Well, surviving this long winter blowing around on his little leaf boat with armies of hungry tits hunting him every day should be right up his street. Have fun James - knock yourself out - no, actually - forget I said that.

Around the site the sallow foliage continues to thin, and the dangles become ever more apparent.

There has been some recent movement from leaves to forks/buds, but until the weather turns colder next week I’m holding off on the naming - I like to be sure they’re fully settled for winter, and they do move in mild weather. A nice variety of colour forms are emerging as usual - I particularly like this fairly common pale form - somehow they seem the best dressed of the bunch - always good to make an effort. This guy seemed rather surprised to see me…

Also Mo is settling down fine in his new home - these fissures work best when they fill with water or are covered in snow. Snow seems unlikely but you never know - water we can rely on - he’ll be wet like this for much of the next 5 months.

I should just stress that over winter this PD is really just record keeping, and as such I don’t expect it to be of much interest to anybody! Not a lot happens - some get predated, some don’t, but I need to keep track of it all and this is as good a place as any. Lots of very similar posts incoming…..

[Wurzel]

Cheers for the photo Ben Come on T-Bone you can do it!!

Have a goodun and stay safe

Wurzel

[David M]

...I should just stress that over winter this PD is really just record keeping, and as such I don’t expect it to be of much interest to anybody! Not a lot happens - some get predated, some don’t, but I need to keep track of it all and this is as good a place as any. Lots of very similar posts incoming…..

Au contraire, Ben, there are plenty of us that find it fascinating, for example the images of the silk trail in your earlier post.

It's also nice to familiarise ourselves with the characters that will keep you occupied through the rest of autumn and the winter.

Bon courage!

[Benjamin]

Thanks as always for your positivity David.

Friday 21st

Some context

The search for hibernators is now in full swing. As mentioned before I cover an area of roughly one square km and search something like 300 suitable sallows within that zone. Particular attention is paid to certain hot spots within that range, but everything suitable is searched.

Searching a sallow via dangling leaves should only really take 5-10mins. Sometimes less, sometimes more depending on my calculation of the likelihood of finding larvae there. This sounds like rather a lot, but split over 2 or 3 days a week for a couple of months it’s quite manageable. Days are short though, and much extra time is spent either locating caterpillars once a dangle has been confirmed or keeping records updated/taking photos etc, so I allow something like 20 days in the field to properly survey the site.

And some more….

Once the survey is completed I only need to gather data on losses, so just 2 or 3 days a month throughout winter are required for site visits, then obviously an intensive period keeping track of them again through spring.

I should just stress that although a thorough survey certainly requires this significant commitment, finding iris cats in hibernation is really not a very difficult task - once you’re in the right place that is, and I suppose that is the really key part. I know my site well enough now to find the 20 most obvious hibernating caterpillars in a single four hour day - it’s searching the extensive peripheral and less productive areas that takes the time.

Dangling leaves and more recently fluorescing pupae make purple emperor early stages really quite straightforward to study - this despite their often extreme low density. I think this is particularly true of the habitat they generally utilise in the UK, as the relatively small, isolated blocks of suitable woodland often containing ride structures that funnel egg laying females to accessible sallows seem custom made to concentrate early stages in areas conducive to study. Another way of putting that is that in these environments female PE’s are forced to lay their eggs at head height (on average) on occasional sallows that occur along our woodland pathways! What more could you ask for?!!

In my study area of one square kilometre I can be very confident I have a good appreciation of what’s where, and from December onwards I’m ‘in touch’ with most of the individuals residing there - imagine trying to do that with any other butterfly species in the same area!!!

As much as I take pleasure in the genuinely excellent hyperbole and seductive imagery that surrounds this insect - the spurning of scientific intrusion, royalty on high looking down on us with utter contempt for our feeble fumblings etc etc - I actually think it might just be the easiest uk species to study - certainly in terms of an absolute study of immature stages residing within these artificially created isolated or semi-isolated colonies. And that’s the point I suppose - send me to Białowieża Forest to get to grips with iris ecology and I’d learn very little in a lifetime, but let me choose a nice block of isolated woodland here in the UK, and I’ll draw you a detailed family tree after a couple of years.

Ok - a bit of an exaggeration, but the unique characteristics of the PE immature stages (creation of dangling leaves pre hibernation and fluorescing pupae) combined with the artificially imposed (by our fragmented landscape) colonial structures that we find in the UK, enable this species to be studied in a way that no other UK butterfly species could be. My site is not perfect in this regard, as although it is somewhat isolated, there are blocks of woodland close enough to promote a fair degree of movement around the wider landscape. Other sites containing PE colonies are totally isolated with hectare upon hectare of inhospitable farmland surrounding them - these sites particularly enable an absolute study of numbers - EVERYTHING within the colony. Even in these simplified environments, the adult butterfly is hard to pin down, and hence the hyperbole, but if we know exactly how many pupae hatched, then we needn’t spend too much time trying to make assessments based on that which we can only really glimpse.

It’s true I’d be more interested to learn about iris ecology in a vast European forest, but investigating how iris exploits our curious modern landscape is interesting in itself.

Of course not all PE sites in the UK fit this description. Vast rewilding projects (eg Knepp) or tree planting projects (eg Heart of England Forest) can host impressive PE populations at a density or over an area too great for this kind of study. Rewilding projects particularly have the potential to give rise to huge population explosions, in the early phase at least, making the normally elusive adults extraordinary easy to observe. Again much has been, and can still be learned about PE behaviour under these conditions, but just as behaviour in captivity must be appreciated as such, I think we should be careful to keep these observations in context.

Anyway - what was that all about?! Winter ramblings. No doubt I’ll have changed my mind again by the end of winter.

So far I have around 40 caterpillars under observation - the vast majority of which are settled in hibernation. Perhaps 10% are still on their leaves - the latest I’ve seen still wandering about was AJ back in 2019 - still active on the 27th November.

Last year they settled a little earlier, this year a little later, but not by much. The incoming cold weather I keep hearing about should give the final few the hurry up they need.

40 this early is promising in terms of numbers, but I’ve searched the easy, productive areas already, so further additions will be increasingly hard work. It is already better than last year though and hopefully I’ll end up with more than the 50 or so from 2019, making this the best year of the 3 so far - we’ll see.

My overwintering data for the select 20 starts from Dec 1st so I haven’t named too many for fear of losing some of my favourite Olympians before they’ve even started. I do already have a few though and I can’t wait any longer to add one more to the stable. What a specimen this one is - for me it has to be Linford Christie. I seem to remember him complaining about references to his impressive ‘lunchbox’. I was only young at the time but even then I remember thinking that I wouldn’t mind if, in later life, I had to deal with this particular issue - as it turned out I never did (because I didn’t become a Lycra wearing sprinter on TV I should clarify - no other reason - none at all).

Linford

Just to clarify the overwintering rules Linford, you can start whenever you like, and there are no banned substances - you’ll be fine. Oh - but it is a marathon and not a sprint - not to worry - small detail. Welcome, and good luck.

[Benjamin]

Yesterday morning was very cold. Arriving on site early it seemed this drop in temperature had given a few stubborn leaf-lovers the final push to leave their comfort zones. It looked like a long cold journey. Last week they were buzzing around in warm sunshine - Seb Coe doing circuits seemingly purely for pleasure, but now it was nothing more than a slow plod.

This year I’ve noticed a few definite dangles higher up. Above 4m is certainly unusual at this site, with 1.5-3m being the sweet spot. Sometimes it’s possible to locate the high ones with binoculars, but even failing this I can be quite confident that a caterpillar is close by if the dangle is the result of definite L3 activity. L2s produce minor dangles that often don’t last long, whereas L3s produce major dangles that can last well into winter or even the following season. Needless to say Linford produced a major dangle unlike any……ok ok - enough already. But major dangles are a thing.

Just to illustrate the process - in the photo above I located the lower caterpillar up close, the middle one with bins and the higher one only via a major dangle. The middle one I probably could have pulled down with my crook, but I no longer feel the need to cause this disruption - especially when the caterpillar has been confirmed with bins. The photo also illustrates nicely the ‘shelves’ that females like to target for egg laying. When in leaf these must make for excellent sheltered landing pads where she can take her time choosing the very best location to deposit her precious cargo. The majority of sallows at my site only produce these shelves fairly low down, but when they occur higher up, and still remain well sheltered, they can still be attractive.

In this one I made contact with the two lower caterpillars but have just noted the location of the other 4. I’m quite sure they’re there, but will only be able to assess winter survival from feeding damage in spring. Only those I have direct access to will be used for month by month winter monitoring.

[Wurzel]

"Seb Coe doing circuits seemingly purely for pleasure, but now it was nothing more than a slow plod." well he is getting on a bit now! Cracking set of images of the cat - love the one where it's contemplating the bud Linford and his major dangle

Have a goodun and stay safe

Wurzel

[David M]

Fascinating information, Ben. Although you claim it's straightforward (and I guess it probably IS once you get to know the location like the back of your hand), it's still impressive how you can track these cats down when they are so high in the trees.

Some nice colours in that woodland. The trees seem to be reluctant to let go of their leaves this year.

[Benjamin]

Cheers David and Wurzel. You’re right David, that winter seemed reluctant to arrive this year, and not only was this reflected in the late autumn colours, but also in caterpillar activity. They have been annoyingly active in recent days sometimes turning up several metres from their last known spot. As you can imagine this makes collecting winter data very time consuming but I do now think they’ve finally settled so I’ve logged their positions and can now hopefully monitor them less frequently.

The 20 for winter losses are as follows:

I will introduce just a few:

Paula Radcliffe:

Paula and her ‘trail’.

When I saw the mess left behind by this one I knew it had to be Paula. Never made it look easy did she, but that kind of determination and grit will serve her well in the months to come. Also she can relieve herself whenever she likes without judgement so for me she’s a dead cert to make it through.

David Stone:

A childhood friend and class mate throughout primary school. I guess we both showed sporting promise early on - he went on to became a serial gold medal winning Olympic athlete and I ended up writing stories about hibernating caterpillars. That’s ok though - I reckon at least 5 people regularly read my posts, and TBH that ain’t bad for a nature blog.

Sally Gunnel

Named after the queen of Essex and now local Steyning resident, Big Sal is an absolute beauty of a caterpillar. Discovered late amongst more dangles than I’ve ever seen a single caterpillar produce, she’s by far the biggest of this year’s stable. Which brings me back to Linford. Poor old Linford is really far smaller than I initially thought. I do consider him a beautifully marked specimen, but he was only really named Linford on the back of the impressive dangle that I detailed previously. He’s actually far too small to be a good Linford, and should certainly have been Jonathan Edwards instead (although whether that dangle would be appropriate for Jonathan one can only guess - I know where I’d put my money though - I don’t think you can fly through the air like that with a ‘megadangle’ weighing you down!).

The difference between Sally and Linford is so striking that I’ve tried to fairly reflect this in a side by side. Little Linford and Big Sal.

The macro and phone disagree on Big Sal - I think her colour appears somewhere between the two in reality

I don’t know if it’s possible to know the sex of these L3 caterpillars but I’d be astounded if Big Sal didn’t turn out to be an enormous female. Testing this wouldn’t be particularly difficult if I were prepared to collect the caterpillars of course, but I’m not, so I’ll have to keep my fingers crossed they survive and I can track them. I must say that at this stage I’d heavily favour Little Linford’s survival chances over Big Sal’s - she looks like a lovely meal served up and ready for the next passing beak, whereas Little Linford melts into his twig and is almost certain to go unnoticed.

So I have the named 20 that I will monitor closely and about another 40 (including 10 or so not photographed and out of reach) with positions logged that will be monitored more loosely.

Finally, having enjoyed messing around on my phone with a new collage app, I thought I’d put a few pics together to showcase some of the captivating variety that I’ve encountered over the last few years. Only low res unfortunately - I’ll get around to a proper job in photoshop at some point. There are also some forms missing that I now wish I’d photographed better at the time but I’m sure I’ll find similar again soon enough…..

L3 variety in hibernation 16

L3 variety in hibernation - 20

[Pete Eeles]

As I mentioned separately, Ben, this is top notch work! I absolutely love reading your posts - so insightful!

Cheers,

- Pete

[bugboy]

It's a good job the victorian collectors didn't possess digital photography, can you imagine the endless list of larval abberations based on the natural variation you've showcased!

[Wurzel]

That variation is brilliant to see, it would be interesting to find out which is the most successful pattern or even if certain patterns work better for different predators, "isn't nature brilliant" (Paul Whitehouse, Fast Show) My personal favourite is from L3 -16 and is column 1 row 2; those two little yellowish triangles give it the appearence of eyes a bit like Sauron that would certainly keep the birds away!

Have a goodun and stay safe

Wurzel

[David M]

Lovely, entertaining update again, Ben.

Your digital collage shows the variation very nicely and demonstrates the range of characteristics one can find in the larval stage of a single species!! Some of the camouflage is breathtaking and one hopes this will keep them safe during the winter months.

[Benjamin]

Thanks very much folks - comments much appreciated as ever.

December losses:

I think I opened this diary around about this time last year and after a few case studies, quickly got down to the serious business of reporting on caterpillar losses.

With Xmas and New Year out of the way it’s that time again and so it was with the usual trepidation that I set out to see which of my sleeping beauties had drawn the short straw during December.

This year the hibernating population is larger than in previous years, with a total of 70 caterpillars made up of those either under direct observation, confirmed via definite dangles, or currently lost having previously been confirmed. The lost category contains those I was unable to locate following their journeys into hibernation, and therefore potentially also includes some that were predated en route. That unknown doesn’t really matter too much, as the 70 just gives me an idea of overall population size, and I only really focus on the directly observable population from now on. In that category I have my 20 Olympians, and a further 25 unnamed.

I was surprised and I must admit delighted to find that only one caterpillar has so far been predated. Inevitably I will pay for allowing myself to enjoy this mercifully low number - bonds will be strengthened and the losses, when they come, will be more acute.

The only loss came in the group of 25 unnamed individuals meaning the Olympians remain complete.

In previous years (focusing now on the 20 named individuals) I’ve lost 5 (2019), and 2 (2020) during December. In both years I had a wider sample that also included December losses. So this year with my highest total (at this stage) of 45 under direct observation and only one loss so far, predation does seem to be well down. Even more encouraging, the one loss was most likely a victim of bronze shield bug activity encouraged by the mild weather over Xmas and so losses to tits remain at an impressive 0/45!

RIP

Very common and active throughout winter in mild weather

Tit numbers do appear to be down, perhaps due to a poor breeding season in the freezing drought of April and the soggy wash-out that was May. Larvae of all sorts were certainly late to get going on the very late leafing trees, so it’s easy to imagine that many nesting birds suffered from food shortages due to sub-optimal timing.

I have also been keeping a close eye on the subtle colour changes that occur throughout hibernation and hope to end up with some completed series come spring. It very much helps to have a large sample to work with for things like this, as many either are not in good positions for consistent photography/do not produce interesting changes/get predated or move etc etc. Alistair (below) ticks all the boxes and I hope, is now in the process of reddening in line with his bud’s development. He hasn’t changed much since the last photo though, and it seems likely that he might settle for this rather sensible compromise between bud and stem colour - we’ll see.

Alistair Brownlee

One of the unnamed 25