mimicry in species

[Susie]

Yesterday at the Sussex BC AGM the guest speaker was Torben Larsen and I really enjoyed his talk (much to my surprise!). He's a really fascinating and knowledgeable chap.

The section I found particularly fascinating was the mimicry between species of butterflies. I cannot remember the names of the species of African butterflies involved but there was one species which was toxic and another species copied its appearance in all colour forms. It was quite incredible.

Apologies for my slightly odd and probably basic questions but I can't help wondering the following:

Why is it more likely for a species to change it's appearance than to become toxic itself? Or is it more likely to change it's appearance, are there any records of a species changing it's food plant to develop toxicity?

The other thing I was wondering about is how likely it is that two similar but separate species could evolve an identical appearance? If species are trying (ok, I know they are not consciously trying, it's evolution, but I don't know how else to word it) to develop the optimal appearance for survival in their environment it is surprising that more species don't look the same, isn't it? Despite a vast selection of colours and patterns the potentially possible the number of patterns that are advantageous to a butterfly must be limited by it's environment which broadly lumps them into larger groups.

I was fascinated to see an African skipper (again I forget the type - sorry) where the upper side looked awfully like a brown hairstreak.

[John W]

Hi Susie, it was nice to see you yesterday! My guess is that toxicity in the adult derives from the larvae eating toxic food plants - in which case, for a non-toxic species to become toxic, it would have to switch its food plant, which is probably a bigger ecological change than just changing its appearance.

Cheers
John

[ChrisC]

there are a few things that get me about this the most basic is how does the mimic know the butterfly its mimicing is poisonous? surely it is pure evolutionary chance rather than mimicry. ( i see mimicry as intentional copying)

[Padfield]

It's quite amazing, isn't it, Susie?

You are right, Chris, that the mechanism is natural selection, but the phenomenon is correctly (by virtue of conventional usage) called mimicry.

'Evolutionary chance' is accurate but a little misleading, however, because it is possible for evolution to be speeded up by various means - notably, through mechanisms that ensure genetic variety, thereby giving natural selection something to work with in each generation. In the case of mimicry in butterflies I would imagine that certain whole groups have evolved to exhibit a certain latitude in markings. That means the 'average' can shift more rapidly in response to selective pressures.

I was very impressed by the mimicry I saw in India last year.

This is my own photo of a common crow (Euploea core), a Danaid:



And here is a blue tiger (Tirumala limniace), also a Danaid:



Amazingly, a single species of swallowtail, the common mime (Chilasa clytia), mimics both of these. One of my students got great photos of the common mime when he went on a school trip to India later in the year.

This is the form which mimics the common crow:



And this one (same species!) mimics the blue tiger:



Incidentally, since mimicry relies on birds trying toxic species and living to tell the tale, you do occasionally see these butterflies getting eaten. I've seen a viceroy in America with a great bite out of its wing and I found these blue tiger wings in India, indicating that something had had a pretty serious go at it...:



Guy

[MikeOxon]

Mimicry is indeed an amazingly complex subject, which raises many questions about evolutionary mechanisms. We know that genes operate on many different levels, like layers, with some genes controlling others. For example, there are common genes in ourselves and insects which code for, say, eyes, but then the genes controlling the details are completely different, so that our eyes and insects eyes have completely different structure!

Several years ago, I photographed some butterflies in India (in the Guest Palace garden in Gwalior) and only realised, when I got home and started to identify them, that I had captured an interesting example of complex mimicry, which is both sex-linked and Batesian. The males of Hypolimnas misippus look like this:

Hypolimnas misippus (male)
Gwalior, India - Dec 1996

The females are completely different and mimic Danaus chrysippus, which is highly poisonous as it obtains toxins from its food-plant - Milkweed.

Hypolimnas misippus (female)
Gwalior, India - Dec 1996

There is a useful article about the various forms of mimicry by Paul Smart in his "Illustrated Encyclopedia of the Butterfly World". He distinguishes between Batesian mimicry, where a palatable species mimics an unpalatable one, and Muellerian mimicry, in which two (or more) unpalatable species have evolved a similar 'colour scheme'. Apparently, there are complex associations, called mimicry rings, where often unrelated species share common patterns to the extent that dissection is needed to separate them!

Once one gets into the tropics, it makes even our European diversity look small!

Mike

[Susie]

Thank you for your replies and photographs. There is so much to think about and learn.

[Piers]

Mimicry occurs across the animal kingdom Sooze, for various ends. Mimicry is of course even used by plants to facilitate reproduction. Mimicry in plants is also used defensively, such as passiflora leaves having structures which mimic the eggs of heliconid butterflies in order to deter the butterflies from laying their ova upon the plant's leaves.

Piers.

[Susie]

Mimicry occurs across the animal kingdom Sooze, for various ends. Mimicry is of course even used by plants to facilitate reproduction. Mimicry in plants is also used defensively, such as passiflora leaves having structures which mimic the eggs of heliconid butterflies in order to deter the butterflies from laying their ova upon the plant's leaves.

Piers.

Wow, that's really blown me away.

I don't know why it should really, as I have known about mimicry for a long time such as bee mimic hoverflies and orchids that mimic insects too, but even so, when I think about it .... WOW

[Padfield]

For no particular reason, Susie, I think you have a copy of Messages from Psyche, a rather lovely coffee-table book on butterfly patterns. It could just be my memory playing tricks on me. But if you do, it has lots of wonderful photographs of mimicry.

It was that book that alerted me to the self-mimicry in tailed blues - their bottom end looks like a head end, replete with eyes and antennae. If you were a bird, which end of this butterfly would you assume was the head?



Answer: The one with the big, highlighted eyes and prominent (not cryptically black-and-white) antennae.

If you don't have the book, put it on your Christmas list!

http://www.amazon.co.uk/Butterflies-Mes ... 1901092801

Guy

[Susie]

Hi Guy, I'll put it on the list as I don't have a copy as yet.

An awful lot of butterflies seem to exhibit that "eye" pattern, don't they?

[Vince Massimo]

Susie, I think you have a copy of Messages from Psyche, a rather lovely coffee-table book on butterfly patterns.

I'll put it on the list as I don't have a copy as yet.

I don't have a copy either . The publisher requested the use one of my photos for the book and I really should have asked for a complementary copy at the time, but now I have to buy it. I was asked to provide this image of a Female Large White, but was never sure in what context it was to be used (or whether it was even used at all).

Female Large White

This has been bugging me for some time, so could someone with the book kindly check this for me, as I am presently too tight to buy it . Hopefully the answer may reveal some other relevant fact relating to mimicry which will mean that my request is still on-topic

Cheers,

Vince

[Susie]

Before I buy a copy I'll be checking out my local library. I am a member in two counties so at least one of them should have it. Use 'em or lose 'em.

[MikeOxon]

could someone with the book kindly check this for me

Vince,

Your image appears at the start of a chapter titled "The Looking Glass", which discusses the nature of perception. It is described as 'an image that we instantly recall from memory after a glimpse of the insect in flight'.

I've not yet read the book in detail but can confirm that it is a very attractive coffee-table book and seems to contain a collection of quite thoughtful essays.

Mike

[MikeOxon]

If you were a bird, which end of this butterfly would you assume was the head?

Intrigued by your description, I have been reading parts of this book. I suggest that your proposed answer to your question does not represent the point which the author, Philip Howse, was making.

He suggests that the double-headed appearance creates confusion in the mind of the bird, sufficient for it to miss its target; i.e. the bird does not strike the 'wrong' head but is quite likely to miss altogether. As I get older, I realise more and more the potential for confusion to delay action long enough for a mistake to be made, so I find this to be a persuasive argument.

Mike

[Vince Massimo]

Vince, Your image appears at the start of a chapter titled "The Looking Glass", which discusses the nature of perception. It is described as 'an image that we instantly recall from memory after a glimpse of the insect in flight'.

Thanks for checking that for me Mike. It sounds like a lovely book, but I generally like to browse a new publication before buying. I expect I will end up getting a copy .

Cheers,
Vince

[Padfield]

If you were a bird, which end of this butterfly would you assume was the head?

Intrigued by your description, I have been reading parts of this book. I suggest that your proposed answer to your question does not represent the point which the author, Philip Howse, was making.

He suggests that the double-headed appearance creates confusion in the mind of the bird, sufficient for it to miss its target; i.e. the bird does not strike the 'wrong' head but is quite likely to miss altogether. As I get older, I realise more and more the potential for confusion to delay action long enough for a mistake to be made, so I find this to be a persuasive argument.

Mike

That sounds very reasonable - my copy of the book is in England so I couldn't check up what he had said. I remember seeing the picture in that book and immediately going off to look at all my own photos of tailed blues.

Guy

[Roger Gibbons]

Living in France, where Swallowtails and Scarce Swallowtails are reasonably common, I have noticed how often a tail is missing. Here is one photo of a Swallowtail that has lost a tail in what looks to be a bite. The butterfly is fairly fresh and the other tail undamaged, so something has attacked and removed the right tail. I mention this in the narrative further up the page.

http://www.butterfliesoffrance.com/html ... Var_5Sep07

I also suspect that 7970 on this page has also lost the tip of the right tail.

I have several other photos of Scarce Swallowtails (e.g. 14738 attached) with missing tails. 14738 is quite fresh and I don’t think the tail loss is due to wear.

It is also true of Two-tailed Pashas (a misnomer since it has four tails) that quite often one tail is missing. The Pasha tails are shorter than Swallowtail tails but still appear to have been removed rather than just wear and tear.

At the end of September a Grayling landed on the ground and was snapped up by a Magpie. Maybe Graylings should start to evolve tails!

Based on my observations, I would say the tails are a very real defence mechanism given the frequency with which they appear have been bitten off, rather than just to confuse a predator.