Benjamin

[trevor]

A very fine looking bunch of athletes there Ben!.
I'm sure there's some medal winners there, for me Gold will go to any
fine fresh female that lands for a few shots. Only ever seen one on the ground.

Stay well,
Trevor.

[bugboy]

That first shot illustrating the camouflage is amazing. I saw it straight away even though I couldn't actually see it without zooming in. Then it just vanishes again as you zoom out.

Glad you're enjoying the White Admirals, all my eggs are in one basket now with just one cat found on my last visit.

[Benjamin]

Cheers Trevor - some will make it but I don’t expect to see them on the wing with such low numbers. At the sites with bigger populations though, and with the effort you put in, I’m sure you’ll get your encounter soon enough…..

Thanks Paul - I never get bored of the amazing camouflage. You do need to try and maximise DOF to do it justice - not so easy in shady settings with a macro lens. Because of these limitations it’s always even more impressive in reality. That particular individual kept disappearing if I looked away to fiddle with the camera for a moment. It’s all in the shapes and the shades - as you scan a mass of leaves you just can’t pick them out, and it’s only when you find them and lock focus that you wonder how it could have been possible to miss them. I’ve lost count of the times I’ve searched far and wide for an individual only to find them exactly where they should have been when doing one final check before giving up.

I’m expecting tracking white admiral to be a challenge when they come to pupate, as I guess they ascend the honeysuckle and wander off into the canopy. For now though, they’re easy. I only have 10 or so (mainly L4) under observation but they haven’t been difficult to find. Feeding damage on honeysuckle is quite obvious, and they always seem to be in similar positions to where the early instar cats are easily found in autumn. If I spend some time looking then I expect to find them so my sense is that the woods must be bursting with them - quite a different experience to searching for PE (in my woods at least).

Just a quick word on small tortoiseshell. I’m keeping an eye on them again this year, but without the mammoth rearing effort of last. That served its purpose well though, as I can follow up some key areas without the requirement for such an investment of time.

On Tuesday over a 250m stretch of prime riverside habitat I counted 60 ST nests ranging from L1-L5. No parasitoids were observed in attendance. I know from my own stock that the primary spring parasitoid Pelatachina tibialis is only just starting to emerge, so many of the early ST batches at this site (currently L4/5) will have avoided it entirely - interesting.

Many butterflies are looking their age but this guy has clearly looked after himself

Pelatachina tibialis

Pelatachina tibialis

I found several peacocks egg laying, so they will be appearing in a couple of weeks.

[Benjamin]

April 24th

Took a quick diversion to keep my ‘April 24th’ series alive. We definitely need some rain, but unlike last year we’ve had some warm weather and avoided frost so things are considerably further advanced. In terms of PE development, they’re well ahead of last year but as always conditions in May will be crucial. As it stands I’d expect to see emperors on the wing in mid June - probably during the third week.

A little more colour if I cheat and move back a bit

[Benjamin]

Just a quick update on the emperor cats……

With so much going on in May I’ve had very little time to keep track of progress in the woods. Or more accurately, with UV pupae searches able to give me the data I want, I’ve switched focus to other projects. I do pop in every now and again though, and today I managed to locate half of the winter survivors. I believe the others are there, but have relocated or were too well camouflaged to be revealed by my fairly brisk scanning search this afternoon. Gone are the days when I would systematically work my way up and down every branch desperate not to have lost one of my few remaining chances of finding a wild pupa.

Development is still in line with my original prediction of a mid June (prob 3rd week) kick off at my site. Other sites are earlier and when pressed by Matthew to name a date I went for the 13th for national KO.

As usual the development gap is quite wide, and although I expect a mid June KO, they will still be emerging well into July. Last week of June should be key.

Unfortunately I will miss nearly the entire flight season away on foreign trips this year, but as I rarely see anything at my site anyway, I guess once the pupae searches are concluded my work will be done for another season.

[Wurzel]

Cracking set of images your "April 24th" set Ben - great idea that

Have a goodun

Wurzel

[David M]

...Other sites are earlier and when pressed by Matthew to name a date I went for the 13th for national KO.

That seems very early, Ben (although I don't dispute the prediction based on the work you've put in).

PEs are overdue a good year. Let's hope this is it.

[Benjamin]

Cheers Wurzel - good to get a series going - I guess the longer it goes the more interesting it could become, and photos are often more useful in such context than subjective notes, memories etc!

No David, you’re right - it’s most likely too early! I think Neil went for the 15th, and I must confess I was probably swayed by Matthew’s 9th at the time. The trouble with predicting national KO is that I don’t know very much about the early sites so it’s always a game of trying to predict progress elsewhere based upon what I see where I am. According to progress at my site the 3rd week of June still seems about right, although the recent spell of particularly cold nights may have pushed KO back a few days. Perhaps 22nd/23rd kind of time would be better. My site tends to be a good few days behind the early sites so probably Neil’s 15th or a few days after would be most likely.

May pupae

Today I made some time for a good old fashioned pupae search. As much as I’m strangely tempted to roll back the years and spend hours searching for PE pupae (Nostalgia? Masochism?), I just can’t possibly justify the time investment when I know that a night time UV search can reveal all with a fraction of the effort. But this year I’ve been following white admiral caterpillars, and as far as I know they don’t fluoresce under UV (will check) so I had the pleasure of an old fashioned treasure hunt. I chose a honeysuckle that had recently hosted two mature caterpillars that I’d successfully followed since autumn, and got to work searching all the routes that I guessed they would likely have taken up into the canopy above their host plant.

Surprisingly it wasn’t long before I found one! I think once again the trusty stepladder was crucial. Being able to get up at eye level with the search area must be a big advantage, as the pupae melt into their surroundings so effectively when viewed from below. I looked for a lot longer for the second but was unsuccessful.

Likely route to pupation

After this I went off to check on a few iris cats. I had rediscovered a winter loss a few nights previously and as he had already headed under leaf and started to fluoresce very strongly I was quite sure that he would already have pupated. This proved to be the case and a very fresh male pupa was discovered - the first of the season.

Spot the pupa….

Interestingly I later found a caterpillar apparently close to pupation but unusually still topside of his leaf! Perhaps he’ll reassess, but to me he looks locked in and close to pupation. He will be very exposed if he pupates where he is, but as I still don’t know what predates them at my site, it’s hard to say whether this unusual choice will advantage or disadvantage him. I’ve certainly had wonderfully concealed pupae disappear almost instantly and apparently exposed pupae survive to eclosion, so I’m reluctant to write him off as a reckless rebel just yet……

The rebellious topsider is located in this very productive iris ride

A full check on the athletes will be conducted next week sometime, when hopefully the majority will have pupated.

[Neil Hulme]

Great report, Ben. I just love that image of the White Admiral pupa dangling high above the path. It gives a real sense of the usually unseen magical world all around us. Every July I stand below an oak, imaging what the view must be like from above, gazing down on dozens of male and female Purple Hairstreaks all basking with their wings open, with the odd male Purple Emperor amongst them. In the absence of wings, a stepladder is pretty useful!
BWs, Neil

[Max Anderson]

Outstanding stuff - White admiral pupae are absolutely stunning, and it's interesting to know that the iris pre-pupae flouresce..

Images are excellent, as usual. I very much appreciate the wide angle shots, showing the habitat and putting the subjects into context.

[David M]

Fascinating stuff, Ben. The effort you put in definitely merits these rewards. It's a hidden world to most of us.

[Benjamin]

Thanks all. I completely agree and find the shots that give a sense of context the most pleasing. I take all these with my phone and carry my camera with a macro lens for everything else. The only problem with this is that although the phone produces the overall effect I’m looking for, the quality is just a bit poor. I really need a compact camera that’s just a better version of my phone. It would be good if I could use it as I do my phone, so holding it in one hand gradually moving in very close to the subject. A large touch screen would be necessary - I guess most modern compacts fit this description so there must be lots of options? I’ll look into it.

[Benjamin]

Over the last few days/nights I’ve been monitoring the commencement of the PE pupation period at my site. I think the majority of the males have now pupated, and the females are following closely behind. I’ve discovered a couple that were previously unknown.

Both the fresh male pupa, and the caterpillar pupating on the topside of the sallow from my last update disappeared soon after I photographed them. The pupa was well concealed and very low to the ground, so I can only imagine it was spotted by something on the ground. The topsider on the other hand, was very exposed to anything above or in the trees so I’d guess it was snapped up by squirrel/bird/bat. As this one disappeared without a small section of the cremaster being left behind (as is usually the case with pupal predation) I’m sure it was predated as a strongly fluorescing prepupa. It may well be that a variety of animals make use of these chunky packets of nourishment. Unfortunately my experimentation with trail cams will have to wait until next year.

In certain light birch doesn’t seem the best choice

Hazel not bad…..

Grey willow is best although I’m not sure about selecting the only yellowing leaf - we’ll see…..

Some of the athletes have disappeared and I’ve so far been unable to locate them with UV. Possibly some have been predated but more likely they have not yet pupated. I’ll have to leave it another week before searching again.

[Benjamin]

On Thursday I spent a very enjoyable few hours under light cloud catching up with activity along my favourite 500m stretch of the Adur. On my return I counted the many small tortoiseshell butterflies and peacock larval nests that I encountered along the stretch.

The final score was 103 - 56 in favour of the peacock nests. Had the sun come out more often then I think the small tortoiseshells might have taken it as I was only really managing to count those that I disturbed from basking along the path, and I’m sure there were many more low down in the vegetation or basking in out of sight areas.

In the small windows of sun, activity along the river was frenetic. Circa 20 thousand peacock caterpillars (mainly L4/5) were feeding as if working towards a developmental deadline that very night, and small tortoiseshells would take to the air en masse with frantic chases of 6 or more butterflies erupting up and down the south facing bank.

It wasn’t just the butterflies that were desperate to make use of these small patches of suitable weather however, and numbers of tachinids are also now building. A few late emerging Pelatachina tibialis were still pesent but new on the scene, and much more significant at this time of year were an ominous number of Sturmia bella. They have 20 thousand peacocks caterpillars in this stretch of river alone to exploit and the speed at which they deposit their eggs all around the nettles surrounding the caterpillars suggest they are certainly out to maximise the opportunity. Of the eggs that are consumed, the vast majority will end up in mature caterpillars, and will therefore likely emerge from the pupa. This doesn’t have to be the case with S.bella but is so often the case that it can be considered diagnostic.

The very first summer brood small tortoiseshell nests are now appearing, but with so much adult activity in evidence it is clear that it’ll be another month before small tortoiseshell caterpillars will take their second turn at dominating the nettles as peacocks are currently. This will time perfectly with the emergence of the much bigger next generation of S.bella (currently entering peacocks at a rapid rate!) and small tortoiseshells will be hit extremely hard (70% infection at this site according to my sampling last year).

What’s interesting about this is that the parasitoid most responsible for impacting summer brood small tortoiseshells doesn’t appear to depend upon the spring generation of the same species to build numbers. I have never found S.bella in spring small tortoiseshells. The most likely explanation for this is that they are locked in an overwintering host and cannot complete their development in time to be on the wing that early in spring. The identity of the overwintering host remains an open question - I thought I had found it but now think I was mistaken.

So as long as peacocks are abundant (I’d say 103 nests in 500m ticks that box) even a small number of S.bella emerging from their overwintering host are able to build a giant next generation (tachinids can lay thousands of microtype eggs) that will time perfectly to exploit the small tortoiseshell summer caterpillars. This giant generation will occur regardless of how small tortoiseshells are faring in any given year. If small tortoiseshells are having an excellent year (as they are currently) then even a small survival rate will result in plenty of butterflies, but if they are struggling as they do in the South East in drought years then this added pressure would likely make summer butterflies very scarce indeed. The multivoltine nature of S.bella ensures that any attempt at further broods of small tortoiseshell are impacted with greater and greater force. By late summer S.bella numbers are so high that in poor years any 3rd brood small tortoiseshell nests stand very little chance of producing any adults at all. This would normally create obvious problems for a parasitoid but as it switches host for the winter, and doesn’t need small tortoiseshell again until summer it would seem to be operating outside the usual regulating pressures that might keep numbers in check.

Although a significant parasitoid of peacocks, there are relatively few S.bella on the wing this early in the year so peacocks can facilitate the development of the big S.bella generation without ever feeling the full force of it.

A more comprehensive understanding of S.bella ecology (ie overwintering strategy) is necessary to further elucidate the picture but it seems likely that in wet years summer brood small tortoiseshell is able to escape this parasitoid by exploiting fresh nettle growth throughout the landscape. Whatever the truth regarding S.bella ecology, it will be most numerous in areas where all its hosts are reliably abundant each year, and likely absent altogether from areas with nettle beds prone to drought (as there will be no hosts to use in late summer). For this reason I believe numbers are most concentrated in the river valleys and reliably damp areas where even in drought years peacocks and summer small tortoiseshells (and presumably the winter host) can be found in good numbers.

This has the effect of further magnifying small tortoiseshell’s well known boom and bust nature, as in wet summers not only are summer adults able to fly across the landscape exploiting a huge amount of habitat that might be completely unsuitable in drought years, but these areas will be relatively free of parasitoids. In sharp contrast in drought years summer adults are forced away from these dry habitats and into the river systems and waterways where large numbers of S.bella will just be emerging from their peacock hosts.

I think it’s illuminating to contrast this with the other main tachinid parasitoid of small tortoiseshell, Pelatachina tibialis. This is a univoltine spring tachinid that overwinters as a pupa. It only requires spring small tortoiseshell caterpillars to complete its annual cycle, and as these can be found throughout the landscape (wherever spring nettles grow) it can be found everywhere. It has only one generation, however, so the small number of individuals that successfully overwinter and survive to emerge in spring have no opportunity to build in numbers with successive broods as we see in S.bella. It may be something of a conservative strategy to remain single brooded when the host is at least double brooded, but it does mean that each year the new generation will emerge in the very best spring nettle beds guaranteed to be suitable for spring small tortoiseshells. In a drying landscape where host summer broods are uncertain this univoltine strategy may well be the best one.

Although I don’t see S.bella being ruinous for small tortoiseshell its arrival here has certainly had the effect of severely limiting summer numbers. And for the reasons described I believe this effect will be most severe in areas of the country prone to drought.

But that’s just the impression that I have from looking so closely at small tortoiseshell in Sussex last year! The full picture is still a highly complex blur and no doubt needs a lot more than a season of effort to bring it into sharp focus.

[Pete Eeles]

Hi Ben - just catching up with your diary, and am in awe ... both of what you've recorded, but also your analyses (and I can't believe the number of larval webs you've managed to find in a 500m stretch - just incredible!). I know how much perseverance and patience it takes to get this level of insight ...great job.

Cheers,

- Pete

[Neil Freeman]

That's a fascinating read regarding the relationships between the Small Tortoiseshells and it's parasites. Really well done Ben.

Cheers,

Neil.

[bugboy]

That's fascinating how S. Bella is able to quickly utilise the available biomass for it's own means. Stuff like this will never cease to leave me in awe as to how ecosystems fit together, and compared to a lot of whats going on right under our noses this is quite a simple 'supply and demand' relationship.

[Wurzel]

Fascinating reading Ben - if you were a betting man what would you go for as the overwintering host of S.bella?

Have a goodun

Wurzel

[David M]

,,,What’s interesting about this is that the parasitoid most responsible for impacting summer brood small tortoiseshells doesn’t appear to depend upon the spring generation of the same species to build numbers. I have never found S.bella in spring small tortoiseshells. The most likely explanation for this is that they are locked in an overwintering host and cannot complete their development in time to be on the wing that early in spring. The identity of the overwintering host remains an open question - I thought I had found it but now think I was mistaken.

A fascinating commentary, Ben, and the above section has really made me think.

The life-cycle of sturmia bella is just as interesting as that of the butterflies it parasitises.

[Benjamin]

Always a bad sign when the diary has slipped to page 2 obscurity…..

Foreign trips not only take up lots of time and require plenty of prep, but also make catching up with local projects once back a frenetic firefighting business that no doubt seems completely absurd to all the friends and family that assume that butterfly investigations simply involve dreamily wandering around the countryside smugly reflecting on another year successfully avoiding the real world.

The truth, as with everything, is that if you want to do things well, then you have to commit to the project. Disappearing for several weeks at the height of the season to identify European butterflies for a living isn’t the kind of commitment that these projects require, but there are obvious benefits and it’s the only way I can justify time in the field abroad (very important to me), so some kind of compromise has to be found.

Perhaps my diary will be more of a winter thing - a good time to reflect and gather one’s thoughts.

Anyway………

As ever thank you all for your very kind comments.

I’ll skip over the iris season for now and pick up on the small tortoiseshell investigations - it’s been an interesting summer.

Wurzel - I hope I’m on the right track and just need to gather the evidence before writing it up. It would actually be something of reasonable interest (I might even be able to start making the case that I’m not just dreamily wandering the countryside….) so I probably should keep my prime suspect to myself for now.

So - small tortoiseshells. Since my last update the lush early summer nettles have desiccated and now look thoroughly shrivelled and unusable.

Even in this river valley this is the case (although there are still waterside patches that could be used) so the situation across much of the scorched Sussex landscape is even worse. Post flowering senescence is perfectly normal of course (although drought no doubt accelerates the process), but what’s missing when compared to wetter years is any form of new growth. With a reasonable amount of rain, and as old leggy nettles collapse, the nettles go again, providing the nutrient rich fresh growth so attractive to butterflies looking to roll the dice. Also under wet conditions the plants direct resources into expansion, with growth continuing throughout the season around the edges of the beds - again providing the ideal resource for further generations. None of that has happened this year, but it’s not clear how concerning a situation this is. It is true that with nettles in such poor condition there is no chance of a third brood of ST, or a few 2nd brood peacocks, but at the sites where I monitor these species (river and elsewhere around the landscape) the nettles were fine until at least late June. Peacock cats did exceptionally well in early - mid June, and summer ST caterpillars would have raced along (leaving aside parasitoid issues for now) in late June and early July. I’m confident even struggling nettles would have been fine for mature caterpillars to complete their development (as a pretty clueless kid I’m sorry to say I’m sure I used to feed them some right rubbish and they always seemed to make it through) and they should have been on the wing in good numbers from mid July onwards. But with nettles by then becoming very poor you wouldn’t expect them to hang around long. Last year at this time nettles were still lush and a good number of butterflies elected to squeeze in a third brood.

Early August 2021

Early August 2022

Of course if a third brood occurs we get another wave of very visible activity around the nettle beds/nectar sources and are left with the general impression that the butterfly is having a particularly good year. Whether this third brood actually benefits overwintering numbers I’m not sure - at my river sites the third brood last year were hit hard by egg parasitoids (leading to small nest sizes) and then by S.bella that by that time was present in very large numbers. As mentioned previously it’s likely that away from these parasitoid strongholds (or in areas without S.bella particularly) another brood could be more successful, and if nettles remain lush throughout the landscape the potential to disperse and escape their enemies increases dramatically.


But anyway, without the third brood it could well be that both peacocks and small tortoiseshells have had an excellent year, and are now safely tucked up in their overwintering sites. When exactly the pathway decision is made (enter diapause/produce another generation) in ST I’m not sure. It seems photoperiod has little to do with it, genetics quite a bit to do with it, and probably various other factors are also more or less involved - the quality of the food plant being consumed by the developing larva, or assessed in the adult stage must surely come into it. Whatever the truth I know for sure that they’re not daft - you don’t get clouds of ST swarming around desiccated nettle beds in a panic with nowhere to lay. And also female batch layers are extremely fussy when it comes to egg laying sites. In spring and summer i’m sure we’ve all watched females testing countless leaves for hours before finally settling on the perfect spot - I somehow can’t ever see them selecting nettles that will desiccate within the month or so that they’ll be needed by the brood. If the nettles give off even the faintest whiff of trouble ahead then the butterflies either enter diapause or, if committed to a next generation, fly far and wide in search of something better - they are highly mobile vanessids after all!