Do butterfly wing patterns really mimic predator eyes?

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By Ella Davies

 

A bumper crop of spikey black caterpillars have appeared on the nation’s nettles this summer.

Clad in velvet coats peppered with white dots, the creatures have been sunning themselves and munching through the weeds in remarkable numbers prompting a flurry of enquiries and reports to the charity Butterfly Conservation.

They might not be so familiar in this form but the insects will grow up to be arguably Britain’s most colourful and recognisable butterfly – the peacock.

As they prepare for their annual Big Butterfly Count, experts at the charity are predicting a bonanza of the butterflies.

Last year, the species surged to third position in the survey which asks the public to record how many butterflies they see in 15 minutes of sunny weather.

Following on from this success, peacocks emerged in good numbers after their winter hibernation according to Butterfly Conservation’s Surveys Manager Richard Fox. The warm, dry weather since the spring has provided ideal conditions for breeding, egg-laying and the development of caterpillars.

“They need to be warm in order to feed and grow and digest their food. Everything about their lives is dependent on warmth from the surrounding world,” explains Mr Fox.

In recent weeks the caterpillars have been entering pupation so the mature butterflies could turn up just in time for the count.

“It could really be the year of the peacock,” says Mr Fox, noting that the two species at the top of the ranking in all previous surveys, the small white and large white, have been seen in relatively fewer numbers this year.

The rich burgundy wings decorated with cream, yellow, black and iridescent violet accents mark peacocks out as one of our brightest species and they are best known for the eyespots they share with their namesake birds.

But according to Dr Martin Stevens from the University of Exeter, everyone’s favourite pub fact about these markings could be wide of the mark.

8 COMMENTS

  1. Shouldn’t there be a link to the rest of the story, explaining Dr Stevens’ opinion?

    I have a buddleia which I grew from seed thirty years ago, and in the last few days it has had an unusually large number of peacocks. For many years i never had peacocks in my garden, but now they have become one of the most abundant species here (Liverpool).

  2. I have issues with many such “pub facts”. In fact I think they contribute to so much of the ignorance around evolution because of the language which implies agency and purpose (e.g. butterfiles evolved eyes on their wings to frighten preditors).

    Of course without asking every preditor why it chose not to eat an insect, it’s virtually impossible outside of a lab to get such definitive answers. Big sacry eyes may be a factor in survival of today’s insects but they evolved for a different reason, or rather for countless different reasons around why the genes that expressed that particular phenotype were selected, not with any purpose to fool preditors. I’m sure sexual selection has had as much if not more of a baring than survival of the fittest.

    Equally one could hypothesise that vertibrate eyes (lets face it, that’s what we mean since compound eyes don’t ever appear to “look at you”) evolved their range of colours, shapes and sizes to mimic other bilatteral eyeilike patterns in nature. all you need to do is think of a benefit and there’s your new “pub-fact”.

    You get them in, I’m off to the gents to think on that one…

    • Big scary eyes may be a factor in survival of today’s insects but they evolved for a different reason, or rather for countless different reasons around why the genes that expressed that particular phenotype were selected, not with any purpose to fool predators. I’m sure sexual selection has had as much if not more of a bearing than survival of the fittest.

      That’s an interesting take. I have to admit the thought never occurred to me. We are all prone to fall prey to confirmation bias and the argument from authority. I admit that I sometimes take something for granted because “such and such study or scientific article said so”.

      But now that you mention it, the “scary eyes” hypothesis does seem anthropomorphic. We are afraid of scary eyes therefore the predators, mostly lizards, chameleons and frogs must be too right? While we’re in the domain of speculating about the predator’s subjective perception of butterflies, what keeps us from formulating the hypothesis that the bright colors of butterflies make them seem even more appetizing to predators?

      Both of these hypotheses are in contradiction with one another but how could one prove or disprove either?

      However I do find the hypothesis of sexual selection more plausible than the scary eyes thing. Bright colors DO make those insects easier to spot by their predators (scary eyes or not). And sexual selection, like in the case of a peacock, seems like a kind of genetic trade-off to favor reproduction and thus survival of the species vs. survival of the individual.

      The fact that insects reproduce in large numbers also tends to support this idea, the survival of the individual being far less important for the species as a whole than large scale reproduction.

  3. If by mimic you mean to copy or imitate closely then no, they don’t. That type of mimicry requires intent and there is no intent involved with evolution. However; if by mimic you mean to simply resemble or to have similarity, then yes. I can see for myself that they resemble eyes, whether or not they evolved that way because of their similarity to eyes or not. That was easy.

  4. Well it shouldn’t be that hard to change perception by eliminate or add colors to the pictures. For an example humans got three different cone cells each of them corresponds to colors such as red, green and blue. Dogs only got Blue and green or that some birds got a fourth cone cell which correspond to ultraviolet light. It’s in general quite rare for animals to have three cones such as in humans so it’s understandable that we humans percieve the pattern which doesn’t justify it’s purpose.

  5. Birds eat butterflies. The eyes look like a cat. Dr Steven’s says that it might be the hissing noise that also puts off predators. Well cats hiss too so I guess that is plausible. If I was a bird I wouldn’t choose to eat anything that looked and sounded like a cat. A win for evolution and the peacock perhaps.

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