Wing-roll behaviour of some members of the Lycaenidae family

[KayG]

That’s great: thanks, David

[Benjamin]

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.

Hi Ernie -

This post popped up in a search for something else but having read it I just want to make a comment. Personally I have no doubt that the wing-rolling behaviour has evolved to direct predatory attacks (particularly crab spiders) away from the vital areas, but I can see the thread is long so I’ll assume there is some debate about this! It reminded me of a video I took several years ago. It’s not a perfect example as the butterfly isn’t really wing-rolling, but I think you can see some slight movement that draws the spider’s attack.

https://youtube.com/shorts/BodHvIbG3zU? ... x6Veu-ABjj

But anyway the point I wanted to make was in relation to your post above. If it is true that this is a solitary behaviour and not something that occurs when butterflies are amongst others, then that observation alone adds a lot of weight to the argument that it has evolved to direct attacks away from the vital area.

The reason that they don’t do it when amongst others is not because of the energy cost, but that in this scenario the last thing they want to do is to stand out amongst the crowd! In a group scenario the chance that you are the unfortunate target is low so not drawing any attention at all is the best strategy. Incidentally I’m sure this is also the reason that you often find individuals of the same species puddling together within a bigger group of several species.

But if you are alone, then the calculation is very different. The chance that you are the target is high and when an attack is likely it makes sense to draw any potential attack to the least important area.

Just for fun it’s also worth noting that as butterflies are very vulnerable when mud-puddling, it would be to everyone’s advantage if they ALL wing-rolled when puddling together! Unfortunately however, the cost of wing-rolling when the majority are not will be so high that this behaviour would never be successful enough to spread and become dominant.

In a scenario where we imagine that all butterflies wing-rolled as standard when together puddling then I wonder whether genes for not wing-rolling would be successful. I imagine they would be, as even though these individuals might break the rule that says they must not stand out from the crowd, there would be many scenarios where they might find themselves next to a single wing-rolling individual (they might even puddle next to such individuals deliberately) and their non rolling behaviour would be rewarded. I would bet that in this scenario not wing-rolling when puddling would be successful enough to spread and eventually become the dominant behaviour. So either way, wing-rolling when pudding is a nice idea in theory, but it seems it is unlikely to occur in our world of selfish genes.