Wing-roll behaviour of some members of the Lycaenidae family

[CallumMac]

Throwing another species into the mix - I saw this behaviour in an Aricia in East Yorks on Friday. Given the location (a historic Northern Brown Argus site, surrounded by Brown Argus colonisations), this was most likely to be a hybrid Aricia artaxerxes x agestis.

[ernie f]

Thanks Callum - the more the merrier I say.

I have never seen a Northern Brown Argus (or a hybrid) and won't get the opportunity to either for some time I would guess so its great when people post their own wing-roll sightings here.

Cheers,

[ernie f]

Under my PD, Wurzel suggested in jest that the SSBs do wing-rolls in my presence as a greeting to me.
Since I am running all suggestions as an open brainstorm - I am going to add butterfly "greeting" to the list. At some point I shall write up a summary report collating all these ideas and post it here.

[Wurzel]

You probably already seen this but it might help you lead to a hypothesis for wing rolling...

https://asknature.org/strategy/wing-sur ... z82d9VKi1s

Have a goodun

Wurzel

[ernie f]

Thanks, Wurzel. An interesting read. Here are my thoughts...

I have recently seen butterflies after days of sunshine and heat do wing-rolls during this heat-wave, so its not to assist the shedding of water at the time, but may be a preening exercise to roughen scales should the need to shed water between the wings arise in future.

Any dirt on the wings sticks to the water spheres and rolls off the wings, but the wings have to be rough for the water to form spheres in order to eradicate these dirt particles. The action of rubbing the wings together may roughen up the wings where they are rubbed, that is between the edges of the fore and rear wings. Why here and only here? Maybe it improves agility in flight. If there is dirt between the fore and rear wings, they may get sticky and not part successfully in flight on turns.

But why is it that only this family of butterflies do wing-rolls to help in the cleaning away of dirt particles if its a problem that all butterflies might suffer? I don’t know, other than it may be an evolved adaptation for this family whilst other butterflies have found other means to overcome the same issue.

Cheers

Every extra bit of info helps.

[ernie f]

A while ago in this thread I mentioned that I had never seen an aged butterfly do a wing roll and suggested it might therefore be something only the newly emerged ones did. I now know this is an incorrect idea as I have recently seen an aged Silver-studded Blue female do a wing-roll.

[ernie f]

Two of the five Chalkhill Blues I saw today at Magdalen Hill were wing-rolling. Last year I scrutinised many from the thousand or so at peak flying time at Old Winchester Hill and only found one that gave a hint that he might do so if there was a good reason to. He seemed to do just one stilted roll then stopped so later I wondered if I had just imagined it as none of the others I saw last year did it. But no. They were doing proper, full-blown wing rolls today at Mag Hill.

Interestingly I had observed this difference with the Silver-studded Blues at Broxhead this year too. When there were a lot of them in a densely packed area such as a lek, the frequency of wing-rolls seemed to reduce (but not disappear) and when there were fewer butterflies in a given area, the wing-roll activity appeared to increase. Hardly scientific it has to be said, but it may be worth further investigation. If it is done to deceive predators, then it may be that they take “safety in numbers” into account somehow. Perhaps if there are a lot of them about, they expend more energy in bouncing off one another than those in less dense areas so conserve energy for this by dropping the time they spend wing-rolling. It is not therefore a conscious decision on the part of the butterfly (I never thought it was) but a natural consequence of how energy is expended in differing circumstances.

[CallumMac]

Not butterflies and birds, but moths and bats: a new study published last week shows that long 'swallow-tails' on some Saturniid moths can jam the echolocation of bats, reducing the moth's risk of becoming dinner.

http://www.sciencemag.org/news/2018/07/ ... ashy-tails

[ernie f]

Thanks Callum - that was interesting. I know the tails on some butterflies act as a visual daytime predator deception but now we also find the same adaptation in moths works the same magic using aural night-time predator deception. Stunning findings.

It got me asking - do any moths wing-roll too? I posted a little while back that I read Peacock butterflies give a warning sound to predators by rubbing their wings together. Maybe some moths give off a warning sound this way too?

[bugboy]

It got me asking - do any moths wing-roll too? I posted a little while back that I read Peacock butterflies give a warning sound to predators by rubbing their wings together. Maybe some moths give off a warning sound this way too?

I think it may be some tiger moths can emit squeaks which cancel out/confuse bat echo location. As for wing rolling, most don't hold their wings in that position and I would imagine it would only be day flying species that would do it if any.

[ernie f]

Bugboy - I know what you mean re moths and wing-rolls. I had the thought because I have seen Silver-studded Blues wing roll with their wings fully open.

Also - re the Peacock and its warning sound. The book I read did not say how exactly how the Peacock rubbed its wings together to make that sound. Have you come across any references to it?

Cheers

[ernie f]

Foreign Hairstreak info from Matsukaze in his post on Wed Jul 11, 2018 7:33 pm

ernie f wrote:
Hi, Matzukaze - love those pics of the Blue Spot Hairstreak.
Incidentally - did you notice if they did a wing-roll? As you are probably aware - my current obsession.

Matzukaze replied:
Yes they did, as did both species of Ilex Hairstreak. I only saw the one Sloe Hairstreak.

[ernie f]

I posted these two pics of a Purple Hairstreak doing a wing-roll on my PD but thought I should add them here for completeness.

[ernie f]

Wurzel adds the following to the wing-roll hall of fame...

ps - Wing rolling - Long-tailed Blue, Lang's and Geranium Bronze all seen wing rolling in Lisbon and Sooty Copper and Dusky Large Blue in Czech Republic to add to the list.

[ernie f]

I also saw a female Brostreak wing rubbing.

Have a goodun

Wurzel

[ernie f]

Summary of forum entries on the wing-roll topic as of 29th July 2018

Its a wet day all day today so I thought I would trawl through the entries people have made regarding the wing roll behaviour of the Lycaenidae family and create a summary to date. I wish to keep this summary as short as possible while maximising the ability for people to comment, debate points, add more observations and thoughts and conclusions over time, so everything here is by numbered list. Please feel free to make a comment or addition on any of the sections below:

1. Name of a species that you see wing-rolling
2. Field obserations of the activity
3. Specific ideas as to its purpose
4. General thoughts on wing-rolling

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 your comments and additions 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 tails 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.
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”. Of course that does not mean there was not one.
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 front 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.

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

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

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

1. Perhaps all butterflies with tails in this family also wing-rolled 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.

I have purposefully not got a section on debate yet as I feel I am still in an information-capture stage.

Best Regards to you all,

[KeithS]

I’d never really noticed this behaviour until I read about it here. Having now watched Common Blues, Chalkhill Blues and Brown Argusisisus all gently “wing rolling”, I get the impression that they do just because they like it. Sun, shade, male or female, the behaviour is the same, and nearly all individuals I’ve watched seem to do it. I thought it might be a defensive thing but I’ve watched them go rolling through bins at 15 feet away where there is no obvious threat, so maybe not. Perhaps it’s just the Lycaenidae equivalent of us stretching our legs after a walk...

[Allan.W.]

Early evening on the local downs in roughly a 1 metre square ,I watched an Adonis male ,a Brown Argus male ,and a female
Common Blue,as they settled they all "wing -rolled" more or less at the same time ,reminded me of birds landing and preening their feathers , its been suggested ,maybe they,re smoothing or flattening their wing scales ……….. I,ve no real theory …..but just a thought.
Regards Allan.W.

[ernie f]

Cheers, guys. The more observations we get on this the better. I have just seen a Common Blue do a wing roll with wings open 45 degrees and with its body angled so that its rear wings were down by about 30 degree below the horizontal (ie not pointing upward).

[ernie f]

Today at Old Winchester Hill, full sun - around 24 degrees, no breeze.

A female Chalkhill Blue landed next to me, opened her wings by 45 degrees and immediately started to wing roll really fast. After 30 seconds or so she stopped. I got even closer and she started up again, very exaggerated and fast.

A little while later further down the path a male Chalkhill Blue landed near me but did NOT do a wing roll. It opened its wings. I got closer and it merely flew off.