Wing-roll behaviour of some members of the Lycaenidae family

[ernie f]

I have mentioned on my PD a behaviour I have witnessed some of the members of the Lycaenidae family perform that I call the wing-roll. Other people who have seen this have their own names for it. I have looked it up but found no references to it so I thought I would open up a discussion topic about it.

My own observations and thoughts can be found in the attached WORD document. I am still in the process of investigating it as I have no firm conclusions as yet. For me - it is an enigma.

The wing-roll behaviour of the Lycaenidae family.docx

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Does anyone have any further observations and ideas about it? Or does anyone know the actual reason why they do it?

All replies gratefully accepted.

[David M]

I have seen Lycaenids do this often but have no plausible explanation for it. Coppers, Hairstreaks, Blues...they all appear to do it by default and maybe you have something with your 'vocalisation' thesis. I will pay more attention to this whilst in France this summer as there is a much wider range of species to observe than in the UK.

It's interesting that both species that open their wings as well as those which keep them closed whilst at rest do it (Green Hairstreaks are constantly at it).

[ernie f]

I have now read the wing-roll study paper (link in post above) a few times and have written my thoughts on it. If interested please open the following attachment.

my notes on the wing-roll study paper.docx

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[MikeOxon]

I must agree that I do not find the 'distraction' theory very convincing. When I look at my animation of a Green Hairstreak, there seem to be very few features that might deflect a predator! It seems to me that a very heavy energy commitment is Involved for very little obvious return.

I think we need to look for a better 'explanation'

Mike

[ernie f]

It appears I forgot to provide the link to the paper I have been commenting on in my last post. Sorry. Here it is.

wing roll study.pdf

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[ernie f]

So far this year I have seen the following butterflies do a wing roll:

Holly Blue
Green Hairstreak
Brown Argus
Small Blue
Common Blue
Silver-studded Blue

I have seen only a couple of Small Copper so far but they did not do it.

[dilettante]

I must agree that I do not find the 'distraction' theory very convincing. When I look at my animation of a Green Hairstreak, there seem to be very few features that might deflect a predator!

Could it not be inherited behaviour from ancestor species with more prominent antennae-like tails? Especially since other hairstreaks have tails (Black and Brown in particular), it seems possible that Green Hairstreak ancestors could have had them too?

[ernie f]

Dilettente

Its possible that its inherited from ancestors - in fact it has to be in some way for them to have evolved this behaviour - but many blues also do it and none have rear wing eye or antennae marks of any kind.

[CallumMac]

If this works, I am attaching a short gif (6 frames) showing a female Small Blue (from the colony at Maryport, Cumbria) performing the wing-roll behaviour yesterday. I can't offer any further explanation as to why she did it!

[Matsukaze]

Large Blue wing-nuggling at Collard Hill today.

[ernie f]

Great stuff.

CallumMac - Your sequence appears to show the Small Blue also moving its middle leg out as part of the wing motion.

Matzukaze - I shall add the Large Blue to my list of butterflies that do it. I'm not going to be able to go that far to witness it myself. Thanks.

[Mazzab]

https://m.youtube.com/watch?v=IyTnM3WK5k8

Just to add to the conversation, I captured this short 18 second video of a Holly Blue ‘wingrolling’ today.

[ernie f]

Mazzab - You have captured it beautifully. Did you notice at the apex of the roll the wings are opened slightly? I have seen this before in other species.

[Mazzab]

Mazzab - You have captured it beautifully. Did you notice at the apex of the roll the wings are opened slightly? I have seen this before in other species.

I’m glad the video came out ok, it was only shot through my phone so quality can be a bit hit and miss. I must admit I don’t think it’s something I’ve taken much notice of before, and just assumed it was to do with cleaning their wings. Will be keeping a close eye on other species from now on to see if I can capture it elsewhere. I wish I’d carried on filming it now though to get the whole sequence!

[CallumMac]

Interesting observation, Ernie. I've spent some time looking in extremely close detail at the photos and I'm not convinced the leg movement is directly connected to the wing-roll - she could equally well just be adjusting her position on the flower. She is also nectaring at the same time, so whatever the purpose of the wing-roll, it is not occupying her full attention!

[ernie f]

CallumMac - Wonderful. This is the first time I have realised they can multi-task!
Seriously though - the observation that they wing-roll while nectaring is important. It completely trounces the idea that they wing-roll as a means of distracting a predator. What butterfly continues to nectar if it knows its about to be eaten!

[bugboy]

Seriously though - the observation that they wing-roll while nectaring is important. It completely trounces the idea that they wing-roll as a means of distracting a predator. What butterfly continues to nectar if it knows its about to be eaten!

On the contrary, this further proves it is a distraction ploy probably primarily aimed at birds (never really any doubt in my mind to be honest). They are at their most vulnerable when active and moving around so a method of distracting any predatory attack away from the head/body must surely become an evolutionary advantage. This simple movement of the wings may look curious and odd to us but when a small bird looking for a quick meal has only a split second to make a decision as to where to aim for, this one act will most certainly lead to a significant proportion of butterflies surviving to live (and pass on their genes) for another day. Tails or no tails it's the movement that does the trick. Most small insectivorous birds only live a couple of years so there's little time for individual birds to learn the trick the butterfly is pulling on them. I suspect false eyes and antennae were a later development once this initial movement was fixed in the gene pool of their ancestors.

[ernie f]

Bugboy - Possible but not proven. They don't always do it, different species seem to do it at different times, some in this family don't do it at all.

I would like to think it is a distraction tactic, but there are certain aspects about it which would seem to be superfluous for this to be solely the case. For example the movement of the wing outward at the apex of the roll in some cases. Why this strange adaptation?

Why is it that the more aged individuals don't seem to do it? Have they done what they know is necessary (mating and egg-laying) and just given up?

I've got to say it perplexes me.

I wish I could be as sure as you are about the solution.

[bugboy]

I think the main issue we have here is that we are over thinking it and coming at it from completely the wrong perspective. This behaviour evolved millions of years before humans came on the scene so to understand it we need to put ourselves in the butterflies shoes. The only biological reason for an adult butterflies existence is to live long enough to procreate. Any trait that enables it to live a bit longer, through natural selection, will be passed on. Look at other aspects of natural lycid behaviour such as always roosting head downward, so the hindwings are more likely to be pecked at first.

If we look at other butterfly families in a similar fashion you quickly see other examples to distracting prying eyes away from the body. Eye spots at the edges of wings in Satyrids, brighter colours of the vanessids wings further from the body (Red Admirals show this perfectly with the body blending into the brownish inner wings. Whenever one of then flies past it's the white spots on the wing tip that catch the eye first).

Slight variations on the theme still result in the same end product, the bird sees the movement and has to make a split second decision into the most likely position of the head. If it pecks at the wriggling hindwings then the butterfly is more likely to survive.

[CallumMac]

I think I'm more inclined to agree with bugboy here. The fact that they sometimes perform the wing-roll whilst doing other things, such as nectaring, might perhaps indicate that it's a passive behaviour performed to reduce the risk of predation when they can't give all their attention to watching out for the approach of potential predators.

I took a photo on the same day of another Small Blue with a big peck out of her hindwing - perhaps an indication that it works! download/file.php?id=124076&mode=view