Wing-roll behaviour of some members of the Lycaenidae family

[CallumMac]

Today at Pinfarthings Banks (Gloucs) I observed a male Adonis Blue wing-rolling vigorously and constantly whilst in cop with a female!

My first instinct was that this lends support to the idea that the wing-roll behaviour is performed as a precaution during times when the butterfly may be less able to evade predation due to other... erm... 'activities'!

The female was tiny... tying together this thread with the other hot topic of 2018!

[ernie f]

Thanks, Callum. You were really lucky to experience that and your pictures of it are pretty good too. I have never seen ANY species of butterfly wing-roll while in-cop and don't remember anyone else saying they had either. Wonderful stuff.

[CallumMac]

Thanks Ernie. This is the third lycaenid species that I have been lucky enough to observe in cop this summer (following close observations of Common and Silver-studded Blue copulations) and like you, it was the first time I've seen wing-rolling during the act. Indeed, I was so focussed on photographing the wing-rolling that I didn't immediately notice the presence of the female!

[ernie f]

Transferred from Ern's Diary - an additional note from Wurzel:

Also for wing rolling; Short-tailed and Provencal Short-tailed Blue and Mazarine Blue.
by Wurzel » Thu Aug 23, 2018 7:43 pm

[ernie f]

A sequence of pics showing a Brown Argus wing-rolling with wings open.

[ernie f]

5th Sep 2018 at Sleaford Heath. Saw a Small Copper do a wing-roll for the first time. It performed two perfect rolls and no more.

Also, same place and time, two more Brown Argus wing-rolling. Again, as before at Broxhead in the last entry they did it with their wings open. Could this be their preferred method?

[ernie f]

I chose the title of this thread with some care but I am beginning to think now that I could be justified in removing the words "of some members".

[ernie f]

I managed to get an 8 burst shoot of the Brown Argus doing a wing roll with wings open and then with wings closed.

Open...

Closed...

Apologies to all Moderators/Administrators - I won't be making a habit of posting so many similar images. If I knew how to merge the sequence into an animated gif I would do that instead.

[ernie f]

Postby Goldie M » Sat Sep 08, 2018 11:54 am

I thought of you the other day when I saw the Red Admiral in my garden, I watched him rolling his/her wings, lots of Bee's and flies were round him so he was doing this constantly and it made me wonder about the Wing Rolling and if this was another reason for it, warding off other insects
I've seen other Butterflies just fly off when disturbed but the Admiral doesn't move, only rolls it's wings.

[Pete Eeles]

Apologies to all Moderators/Administrators - I won't be making a habit of posting so many similar images. If I knew how to merge the sequence into an animated gif I would do that instead.

You can post videos too

Cheers,

- Pete

[bugboy]

Here you go Ernie I use PhotoScape X but I imaging most photo editing programs can do this.

[ernie f]

Bugboy: Thanks for creating the animations for me. They are great. In fact they are actually better than I remember because of course when its happening you are 1/2 thinking about how best to take the picture and only 1/2 seeing what is really there!

Pete: Thanks for reminding me about videos. I tried to upload one once but could not do it from my laptop.

[ernie f]

Discussion on the wing-roll topic as of 27th September 2018

I am nearing at the end of my posts on UK butterflies for 2018 so it’s time for a recap and discussion about my wing-rolling findings.

This summary is copied to both my own PD and the general topic section called: Wing-roll behaviour of some members of the Lycaenidae family.

Please add any comments and additions you may think of under the general topic so it keeps things neat and in one place. Thanks.

1. Wing-rolling Species list

I have not seen all these species do it but others on this forum have reported they have.

1.1 UK

1. Small Blue
2. Large Blue
3. Holly Blue
4. Common Blue
5. Adonis Blue
6. Chalkhill Blue
7. Brown Argus
8. Northern Brown Argus
9. Purple Hairstreak
10. Green Hairstreak
11. White-letter Hairstreak
12. Brown Hairstreak
13. Small Copper

1.2 Elsewhere

1. Common Posy
2. Blue-spot Hairstreak
3. Ilex Hairstreak (both species)
4. Long-tailed Blue
5. Lang's Bronze
6. Geranium Bronze
7. Sooty Copper
8. Dusky Large Blue

2. Observations

1. Some species do it only with wings closed (eg Green Hairstreak), others with wings open or closed or even ajar (eg Silver-studded Blue). I have seen a single individual SSB do a wing roll with wings closed then moving to do it with wings open.
2. Some species who have “tail” projections on their hind-wings are known to wing-roll (eg White-letter Hairstreak), others without tails also wing-roll (eg Small Blue).
3. Both males and females do it.
4. Whilst wing-rolling can occur while the butterfly is doing something else such as nectaring they also do it when they apparently are doing nothing but perching.
5. They will do it while perched on something or simply standing on the ground.
6. I have not seen them do it while roosting, egglaying or mating (although one forum observer has reported seeing it done once during mating).
7. Butterflies of all ages do it. I have seen a newly emerged SSB and a faded old SSB do a wing-roll.
8. The frequency of wing-rolling can be slow (almost leisurely) or fast (with some vigour).
9. They are more likely to wing-roll when first perching after flight (but they can and do perform it at other times).
10. I saw one SSB do a wing roll for 40 seconds and then he stopped for at least 5 minutes. In that I time I did not approach and I could see no other external “cause”.
11. They wing-roll in sun or when it is overcast.
12. Sometimes the wings open slightly at the apex of the roll.
13. The fore-wings of SSBs can part as well as the rear ones when wing-rolling but they keep the rest of their body as still as possible.
14. Small Coppers do not do it so readily and when they do, it seems to be slower and with less actual roll.

3. Ideas (Open Brainstorm – no analysis, other than to arrange into groups of similar ideas)

1. Itching/preening/cleaning/scale alignment/scale roughening/parasite removal
2. Keeping balance
3. Greeting/mate attraction/ant (or other symbiote) attraction
4. Wing flexing/Improving agility in flight
5. Agitation
6. Enjoyment/pleasure
7. Predator distraction/redirection/audible or visual warning (not just birds, but dragonflies, lizards, mantids, spiders, etc)

4. Supporting Thoughts of forum members (Open Brainstorm - no debate)

1. Perhaps all butterflies with tails in this family also wing-rolled at one time but some evolved to lose their tails.
2. Perhaps there are two evolutionary tracks, one developing tails, the other developing wing-rolls and some developed both.
3. When and for how long and what frequency wing-rolling is performed could be dependedent on how “safe” a butterfly thinks it is – how much risk it is under.
4. When and for how long and what frequency wing-rolling is performed could be dependedent on how much or how little energy it has at the time.
5. There appears to be less wing-rolling going on when there are more individuals in a given area, perhaps wing-rolling activity decreases as population density increases. Safety in numbers may be a factor which regulates the activity.
6. Keeping still might be a better predator evasion technique than moving wings.

5. Discussion

This section is to provide my own thoughts on wing-rolling given the information collected above. I’ll start by going through the Open Brainstorm Ideas from forum members, interleaving them with the Supporting Thoughts of forum members where they seem appropriate.

I’ll go through each point in turn to try and argue against it and see what’s left. To quote Arthur Conan Doyle’s sleuthing character Sherlock Holmes in his book “The Sign of Four” – “When you have eliminated the impossible, whatever remains, however improbable, must be the truth”.

Item 1: Itching/preening/cleaning/scale alignment/scale roughening/parasite removal

Unlike a bird preening its feathers the butterfly cannot be selective. The bird can chose which feathers to preen with its beak. The butterfly only has the ability to rub its wings together. It is doubtful that this would have the result to align scales on its wings, and if it did it would only be those few where the wings come together. It is the hindwings that are rolled and mostly the forewings are held still. Thus the forewings are never “preened”. This would seem wholly inadequate as a scale alignment technique as two of the flight wings are hardly touched. Plus in those species that wing-roll with wings wide open, its only a small portion of surface area where the fore and hindwings overlap that will be rubbed together. Likewise cleaning and parasite removal can be dismissed I think. Why would the butterfly wish to clean or remove parasites only from its hind-wings or a small portion of its forewings? And the undersides get virtually no such attention in the process of course. I think we can safely dismiss this option.

Item 2: Keeping balance

I have seen butterflies that are completely still, suddenly start to wing-roll without otherwise moving from their perch. I have seen the reverse too, butterflies that are wing-rolling suddenly stop and don’t move. If wing-rolling was for balancing purposes you would expect some shift in posture. Also I have seen a Silver-studded Blue wing-roll really fast for some time while perched solidly on the ground. There was for example no wind breeze in this situation which the wing-roll might be used to balance against. So in this instance they are clearly not using the motion to keep balance. I think I can safely propose this is not the reason for wing-rolling.

Item 3: Greeting/mate attraction/ant (or other symbiote) attraction

I have studied the aspect with ants in some depth but won’t repeat the details here. In summary, whilst there are some wing-rolling butterflies that do have a close relationship with certain species of ant there are equally butterflies that wing-roll that have no known association with ants.

Most of the time I have witnessed wing-rolling it has been with individuals that are not close to others of their species. In fact my observations suggest they do it more when isolated from others and less when they are more densely packed such as in a lek situation. So I think I can rule-out wing-rolling as a method of greeting.

However, I cannot yet completely rule out mate-attraction. We know that some butterflies use pheromones to attract members of the opposite sex so it could be that wing-rolling is one way this family of butterflies emits or distributes such volatile chemicals. I am very cautious about this though because the wing-rolling is performed by the hind-wings whereas the pheromone emitters are on the fore-wings. Also both males and females will wing-roll. Alternatively it might be a visual display rather than an olfactory one but again I am cautious because on the three occasions I have seen Small Coppers wing-roll, it has been of very short duration and very slight movement. You might imagine a visual display would be more pronounced than that.

I think the observational evidence that I have gleaned so far suggests that all three aspects of this option are unlikely to be true.

Item 4: Wing flexing/Improving agility in flight

As mentioned above, the Small Coppers that I have witnessed wing-rolling do so only slightly and sparingly whilst others such as Silver-studded Blues can do so with gusto and at length with wings held open as well as closed, sometimes moving from one wing-setting to the other without a noticeable break. I find it difficult to believe that butterflies of the same dimentions and often the same habitat and in the same family would perform the action with such widely different styles. Surely they would all wish to have the same level of airborn agility.

I have also noticed that more often than not a butterfly will perform a wing-roll just after landing rather than just before take-off. If it was for airborn agilty one might suppose the opposite to be the case.

I do not therefore think they are flexing their wings as a strengthening exercise or other form of preparation to be more agile when in the air.

Item 5: Agitation

Now things get a little more difficult. How can you tell if a butterfly is agitated or not? I reported above that I saw one SSB do a wing roll for 40 seconds and then he stopped for at least 5 minutes. In that time I did not approach and I could see no other external “cause”. Of course that does not mean there was not one but I was particularly attuned to this prospect at the time. If he was showing agitation for 40 seconds you might have expected him to move from his perch, or perhaps flit about a bit afterwards, but he held fast for at least 5 minutes after the wing-roll. I know this is just one example and you cannot generalise from one observation but it does suggest he was not agitated while he was wing-rolling.

Also when males come together to spar over territory you might expect them to be in a heightened state of agitation and yet I have never seen males wing-rolling while resting on the ground between such bouts when in close proximity to each other. You might imagine if wing-rolling was due to an agitated state, males would be wing-rolling in one another’s presence all the time.

I suggest we can eliminate this option too.

Item 6: Enjoyment/Pleasure

If understanding an emotion like being agitated was hard enough, can we know when a butterfly is feeling pleasure? How can we even know if that is even possible? Is it ever apparent from observation?

Higher life-forms (if we can call them that) can be shown by observation to perform acts they find pleasurable. Obviously primates, but also dogs, cats, dolphins, parrots… How far down the chain can we go? All I can say is I have never observed anything (other than wing-rolling) that could be construed to be a pleasurable activity in butterflies (not even the act of copulation!) and of course it seems only those from the Lycaenidae family do it. One might imagine that they are not more advanced than any other kind of butterfly, so if its for pleasure, why don’t all butterflies wing-roll?

I would suggest this is a reason we can rule this out but its not hard evidence of course.

So we are left with…

Item 7: Predator distraction/redirection/audible or visual warning

This was always the default hypothesis, the one we judged all others against. Although I have (at least to myself) ruled out all other options – it is worth probing this last option in detail because its is not as clear-cut as it might now seem.

Its really all about avoiding predation but this option incorporates two aspects. I’ll start with the predator warning-off aspect.

Does the process of wing-rolling make some kind of audible sound – a warning sound that we humans cannot hear? I have read that Peacock butterflies can rub their wings together to make such a warning sound so it is not unprecedented in the butterfly world. Could it be a visual warning? Some butterflies flap their wings to reveal startling patterns and shapes on their wings to frighten-off would-be predators or at least make them hesitate long enough for the butterfly to fly off relatively unharmed.

In both cases I am doubtful. None of the Lycaenidae (in the UK) reveal startling patterns when they roll their wings and our friend the Small Copper is very stingy with its roll, doing it so slightly I cannot imagine it makes any sound at all – certainly not one that would be effective in warding off predators.

And now a discussion on the predator distraction/redirection aspect.

There has been one study to my knowledge that purported to conclude this indeed was the reason for wing-rolling but without going into detail I am afraid I have found all sorts of reasons why that scientific study is questionable, in its set-up, performance, data collection/analysis and therefore its conclusions.

So to my mind the issue is still open to dicussion. So what are the arguments and is there any bulk of field evidence one way or the other?

One thing I have to emphasise from the outset is the difference between tailed butterflies and wing-rolling ones in this family. There is a tendancy to believe that because one factor points to predator distraction/redirection therefore so must the other, but the two are in fact mutually exclusive. The tail-like protrusions, eye-shaped patterns and bulges to the rear of some members of this family even to our eyes resemble the front-ends of the butterfly to varying degrees depending on species and clearly are utilised to distract predators to attack the rear end of the butterfly, allowing it more chance of escape with only superficial damage to the hind-wing edges. For example, some tails of some species look exactly like antennae, although it has to be said others are less well-formed and to us at least, less convincing.

It is also clear that some of these “tailed” butterflies who also wing-roll give the effect with the movement of these tails as though their antennae are moving and so look even more like the front-end of a butterfly to a predator. But the butterfly design and its behaviours are independent of each other. There are many butterflies in this family that wing-roll that have no “tails” or “eye-patterns” at the rear, for example the Small Blue.

One suggestion was that all butterflies with tails in this family also wing-rolled originally but some evolved to lose their tails. I do not think this is the case because of the additional benefit to those who do both. The more convincing the subterfuge the more likely the butterfly will survive to mate and so the more likely the survival trait will continue to the next generation and perhaps be enhanced as it evolves rather than become redundant and lost.

So it appears what has happened is that two originally independent evolutionary tracks in the same family of butterflies crossed-over and combined in certain species. We have the tail-and-eye evolutionary track and we have the wing-rolling evolutionary track and in certain species like the White-letter Hairstreak, they reinforce one another to better fool a predator. But they are still separate traits.

So in our discussion on wing-rolling behaviour we should dispense with tail-and-eye design and consider the wing-rolling behaviour in isolation.

A key factor in wing-rolling behaviour appears to be the reluctance to do it when close to others of the same species. Even in lek situations my observations suggest the butterfly appears to do it when it is not relating to a neighbour in any way (probably because it is unaware of its neighbour’s presence at the time). It appears to be almost exclusively a solitary behaviour (the one observation of wing-rolling in a mating couple being the exception to the “rule”). This to me suggests a butterfly that is surrounded by others believes itself to be relatively safe in numbers and because wing-rolling expends energy which might be better utilised finding a mate, sparring with rivals or fending off suitors, it conserves energy in this situation by not wing-rolling. If this is the case then the conclusion is that wing-rolling is performed as a positive action to fool would-be predators when the butterfly considers itself to be at greater risk.

However the counter-argument is that it would seem that either keeping still or flying off would be a better strategy when faced with a predator. Now obviously this is the case because I have witnessed both these scenarios on my approach to a butterfly in this family. For example Small Coppers set their wings ajar ready for flight but stay still OR just fly off anyway if I merely walk straight up to them. But there is the scenario where the butterfly is not sure if there is a predator about or not. It knows something that is nearby might be, but cannot see what it is. It is not certain. Maybe it feels a vibration but thinks it might just be a nearby fern blowing in the breeze – who knows. The wing-roll in that circumstance is a useful behaviour to distract/redirect a “potential” predator that it is unsure is there.

I have seen hundreds of individual butterflies in a species I know will wing-roll when needed which did not do it while I watched. I once followed a Silver-studded Blue for over 30 minutes while it flitted about and not once did it wing-roll. I have done the same with Small Coppers and Chalkhill Blues too with the same result. However in all these cases, the butterfly was one individual in a large colony. The Small Copper was in a lek of 20 to 30 individuals, the Silver-studded Blue in a lek of 50 to 100 individuals and the Chalkhill Blue in a vast colony of over 1000 individuals.

They don’t do it when they know for sure that a predator is advancing (they more often just fly off in this case), nor when they know there is not one (they just carry on what they were doing in this case), nor when there might be one but the chance of being picked-off in a crowd of others is less likely (as in a lek/colony situation) - they do it when there is a higher degree of uncertainty that a predator is nearby in a time when they perceive they are at higher risk of predation. Obviously there is some dependency between these two factors. For example the more certain you are there is a predator the more at risk you will feel, but these two factors do operate separately. It may be there is no predator around but at the same time you may feel you are in a higher risk environment.

To add some confirmation to this idea - why can wing-rolling be done slow or fast by the same species, eg the Silver-studded Blue? Could this be because the butterfly who does it fast feels more at risk? I think this is a strong possibility. There was a day when I saw one SSB doing a slow wing-roll close to the edge of a lek while perched on a heather bloom. A moment later I espied another one out in the open on a sandy expanse of ground well away from the lek and this one was wing-rolling furiously. There was no predator near it but it was certainly sitting in a risky position to be predated if one had been close by. There was no cover anywhere close to it.

Many is the time I have seen a butterfly wing-roll on landing. It might be suggested this is a time when it is at high risk of predation because it may have inadvertantly landed near a predator, so evolution is edging toward this becoming an automatic behaviour on landing in some species. I have for example seen Holly Blue’s do this.

There is only one last thing I have witnessed that I cannot fully explain and that is why do the wings part slightly as a component of the roll in certain species, eg Silver-studded Blue? That fact I cannot explain it may just be because I am not familiar enough with the butterfly’s anatomy in such an instance. It could merely be that the way the wings operate normally in some species causes them to part on the apex of the roll, not because it has any specific purpose. I just do not know.

Taking everything into account I conclude that wing-rolling is to do with predator redirection and it tends more to be an active response than a passive one although evolution may be operating to move it to be a more automatic behaviour in some species while not yet in others.

I mentioned the published scientific study above which tried to prove this theory (it is referenced in an earlier post) and whilst I do not think they succeeded in their proof, that does not mean I think what they were trying to prove is wrong. The weight of observational field evidence tends to support the hypothesis I believe. I have finally come off the fence in support of this theory.

It remains to devise a better, more definitive test that will prove it.

Appendix 1: Uncertainty/Risk Decision Table

Definitions

A butterfly understands its level of risk as to how prone it is to predation in a given circumstance. If it is in a community of many other butterflies its risk reduces. If it is hidden amongst foliage its risk reduces. If it is out in the open on its own – its risk increases. If it is otherwise occupied/distracted, its risk increases. And so on. The level of risk it perceives is independent of whether there is a predator actually in its vicinity or not.

A butterfly will have a degree of uncertainty as to whether or not a predator is nearby and is stalking it. Even when there is no predator nearby the uncertainty can be modified by events such as falling twigs near to the butterfly, sudden shade cast over it, the vibration of footfall of an approaching butterfly enthusiast trying to get its picture! All of which serve to decrease the uncertainty. It can of course only be 100% certain when a predator actually attacks it otherwise its uncertainty is somewhere along a scale.

[ernie f]

Noise made by Peacock butterfly.

Its not Lycaenidae but I mentioned this in the brainstorm list. I have been looking back through past posts on the general topics and came across this thread from 2006 which is of interest...

start thread

by Steve Skingsley » Tue Feb 28, 2006 2:44 pm

I was moving some logs during the winter when I came across a peacock butterfly, which I assume was hibernating. As I looked closely it flashed its wings open and made a shhh sound. It continued to do this for some time.

by Pete Eeles » Tue Feb 28, 2006 6:03 pm
The Peacock makes this sound by rubbing the forewings and hindwings together.

by Adrian Hoskins » Sun Mar 05, 2006 6:05 pm
The noise made by Peacocks is well known, and happens when the butterflies rapidly open their wings after being disturbed. It appears to be a sort of warning noise, which accompanied by the sudden appearance of the "Peacock eyes" is probably effective in momentarily scaring a predator, and allowing the butterfly to escape. Sometimes however, Peacocks are seen with peck marks where birds have attacked the false "eyes", and in this case it is thought that the "eyes" have a secondary function in that they divert a bird's aim towards the "eyes", and away from the body of the butterfly.

end thread

No Lycaenidae wing-roller appears to make this audible sound that I know of but it is interesting that other butterflies have their own version.

Its also interesting that bit about the bird-pecked false "eyes".

[ernie f]

While reviewing my recent entries on my PD I found I had forgotten to transfer this snippet of info....

" I saw one Small Copper on the ground with its wings up do a very definite, single wing-roll! It was as good a wing-roll as any Green Hairstreak or Silver-Studded Blue might perform, but it was a single roll ".


I add it because it was only the second time I had ever seen a Small Copper do this and the first time was not too definite.

[ernie f]

From time to time I'll add any wing-roll stuff I come across that is new to me. I saw these two Brown Argus at St Catherine's Hill. They were chasing one another for a good while before landing together. The one on the right then frantically wing-rolled at the one on the left with wings open.

[Pete Eeles]

I've been reliably informed that the great Jeremy Thomas refers to this behaviour as the "Lycaenid Shuffle"

Cheers,

- Pete

[ernie f]

I am adding this from a note Wurzel made in my PD. He said...

"Having just got back from Portugal I can let you know that you can add Lang's Short-tailed Blue, Southern Brown Argus, Iberian Sooty Copper and Southern Common Blue to the wing-rolling list".

Thanks Wurzel.

Note - if anyone has any further observations on wing-rolling please feel free to add them under this topic.

[ernie f]

I have being going back through my hand-written records about Silver-studded Blues while I compile my report for them this year and discovered a hand-written note I made last year to myself about seeing a male SSB wing-rolling while in-cop, similarly to a previous note that Callum made on this thread about his observation of Adonis Blues doing the same. He had pics but unfortunately I didn't which is probably why I forgot to record it here.

[ernie f]

This year a fresh female SSB (still with wobbly wings from not being fully "pumped-up") was doing a wing roll. However its method was odd in that it held its wings ajar while it did it, almost as though it was not yet able to close them? I created an animated gif for it but couldn't upload it because no matter what I did it was too big.

Here is a three-step still sequence instead.