Question that's been bugging me!

When I was doing more moth trapping 20 years ago, one question arose in my mind to which I’ve never had a satisfactory answer (and I’ve tried it on various people over the years).
Why are moth ‘plumages’ generally so stable?
Presumably most moths evolve so that they are well camouflaged (except for a few which have warning colours). In birds, the plumage is presumably an important factor in attracting a mate, so an aberrant male might have more difficulty in attracting a female. But in moths, well certainly the strictly nocturnal species, females attract males by emitting pheremones. The male moth will [attempt to] mate with a wodge of cotton wool if it smells right! He won’t be put off if she doesn’t look quite right - and presumably the same applies to the female if approached by an odd looking male.
There is of course some variation in moths of the same species - but not very much. If you look at all the swallow-tailed moths in the gallery, there is little variation.
I can see no evolutionary reason for this stability in moth design.
If anyone is looking for a PhD topic, I’m pretty sure that it hasn’t been done!

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But you said that most are well camouflaged so any that have somewhat different pattern/colour is less well camouflaged and more likely to be eaten so won’t pass on their genes.
There is also the question of colour in fungi, why are they coloured at all and why so many different bright colours.

In the case of fly agaric one might speculate about warning colouration. (Wikipedia’s article describes aposematism as a thing found in animals, but I don’t see any particular reasons why it couldn’t occur in plants or fungi.

True - but that doesn’t really explain why, for example, a green carpet couldn’t have more variation in its pattern. Would it make it more vulnerable if it had a smoother cross-line for example? Or the black triangles on the costa were placed differently?
Interestingly, there are species which are quite variable - July Highflyer for example. So what is the competitive advantage for green carpet in having so little variability?

If it ain’t broke, don’t fix it?

I don’t understand the point you are making?

If the current colour scheme is effective in, for example, protecting from predation, then there is no driver towards change.

The absence of a driver towards change is insufficient - you need something actively preventing change (such as stabilising selection)

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there are lots of citations for this paper, some of them might help with understanding the original question. might need to look at the mechanisms for creating the patterns and colours

Thanks for that, Mike. Very interesting.
Understanding the mechanisms that drive colour diversity between moth species is potentially relevant. But it doesn’t really explain what the competitive advantage is to a particular moth species to stay colour and pattern consistent.
A sub-question is why so many of the Noctuidae retain the kidney mark and the oval mark. Did or do they have some significance in survival terms?
Perhaps one of our younger members will dream up some relevant research!

I wonder if there is no competitive advantage but rather a quirk of the molecular system i.e that it is ‘difficult’ to have the small changes that would give the kind of slight variation you are looking for. Does not mean many other aspects of the moth could have slight variations. This might be nonsense but something to investigate to see if it is nonsense!

But that seems to contradict the case of the peppered moth where it changed its appearance dramatically in a short time-frame!

It is a while since I read about it, but I recall a theory that the genetic change in the peppered moth was not driven by predation selection pressure, but by the effects of metal pollution directly on the chromosome. Peppered moth got all the attention because it made a nice story, but other species also changed colour, some in the opposite direction - they became less camouflaged. It was written up by Geoffrey Fryer in The Naturalist about 15 years ago.

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I realise that this is an esoteric question, but I just happen to find it fascinating.
One thing I wondered is whether any research has been done on moth vision. More specifically, what can they see at night. Obviously, in total darkness they cannot see anything. But perhaps they can see more in low light than one might imagine - for example some species seem to be able to take evasive action when a bat approaches.
I think this might - just might - be relevant to my basic question on these grounds: supposing that moths can see the pattern of another moth to some degree in very poor light. Then pattern could play a part in mate selection; and that could be the driver away from pattern changes. Is it possible that a male moth can see things in a female moth’s ‘plumage’ that humans cannot?

There is quite a bit of webstuff

Another thing that has not yet come up are those moths with Antenna that look like old TV aerials.
It was once calculated that the spacing of the hairs on them matched the wavelength of the sonar of bats.
The light is often related to direction of travel where natural light from the moon and stars act like a compass. Moths that use this technique fly in ever decreasing circles when they encounter an electric light.

That second article seems to me to shed quite a lot of light on my original question! Thanks, Derek.

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OK, looking at the ‘vision thing’, I realise that micromoths show a lot more variability than macros (in general). According to Michael Majerus in ‘Moths’ (Harper Collins 2002), the number of facets in a moth’s eyes varies enormously - ranging from 27,000 in the convolvulus hawkmoth to 200 in small micros. Could there be a link here with large hawkmoths showing little if any variability while a moth such as Epiphyas postvittana is very variable?

This is an interesting discussion!
I suppose that we also have to remember that we’ve only been taking a close interest in this sort of detail for a couple of hundred years - the blink of an eye in evolutionary terms (at least for most macro-organisms).
I recall those Victorian cabinets, full of pinned specimens of butterflies, with examples of every aberration they could find. Has over-collection affected the populations of those aberrations (as it is said to have done with no-longer-quite-so Sweet Violet)?
But there is evidence that anthropogenic effects (persistent organic pollutants, climate instability, ionising radiation) are already affecting the genetics of many species: though I suspect that any plumage/markings changes will only represent a small fraction of the overall impact. Our descendants may see more of these than we have.

Might be nice to see a set of same species moths from the trap ideally all lined up like in those victorian cases but suspect the (live) moths may not cooperate so just a set of individual photos all arranged so they can be compared in detail. There may be parts of the pattern that are not so similar as it seems on initial inspection.