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Which way up to read The Map?

The common map (Cyrestis thyodamas) Doi Chiang Dao

It has been suggested that the Common Map butterfly (Cyrestis thyodamas) – also called the Oriental Map – relies for its survival on resting in an upside-down position (1, 2). Or creating the illusion of facing the other way.  If this is indeed the case, then it is not so much a form of camouflage as a way of deflecting attacks by would-be predators, such as birds. The most common type of attack deflection device used by butterflies is the eyespot, although there is considerable debate among researchers about the effectiveness of eyespots as anti-predatory devices (3). Nevertheless, most butterfly photographers will be familiar with images of apparently healthy butterflies with what appears to be evidence of a nasty peck on the eyespot (below). In other words, a narrow escape!

Palmking (Amathusia phidippus palawanus) with damaged eyespot

Features – and behaviours – which create the illusion of an organism facing in the opposite direct are called ‘reverse mimicry’ or ‘symmetry deception’ (3). False heads are good examples of this and there are many butterflies which utilise reverse mimicry by creating the illusion of antennae at the end of their hind-wings. The trick works by both deflecting the attack and allowing the butterfly to escape: in the opposite direction that the bird, lizard or preying mantis may have been expecting!

In this case however, it is – I think – suggested, that as well as adopting a reverse mimicry, Cyrestis thyodamas is also creating the illusion of a moth. This form of camouflage is best described as masquerade – although quite why it is more advantageous to look like a moth rather than a butterfly, is not clear to me since moths get eaten just as often. Maybe it is just an advantage to be able to look like a butterfly one way up, and a moth the other way up! Most insects use masquerade mimicry to look like something inedible or unattractive, like a butterfly looking like a leaf, or a caterpillar looking like bird droppings. (3) In this case, perhaps the Common Map butterfly just needs to look like something that gives the impression that it will fly off in the opposite direction?

There seems to be no question that Cyrestis thyodamas sometimes adopts an upside down position (below), but the effect would also work if the butterfly was resting on the ground, i.e. seen from above. I would welcome the opinion of other observers and photographers of this species whether they think it looks like something upside down?

The common map (Cyrestis thyodamas) resting in an upside down position above a water culvert. Doi Chiang Dao, Thailand

There are many examples of animal-like patterns on the wings of butterflies and moths: from toads and owls on the undersides of owl butterfly wings, to flies on the wings of Macrocilix maia. We must remember though, that however convincing these pictures look to our eyes, they may not appear the same through the eyes of a bird. They may work just as well by startling a predator, rather than convincing it that it really is an owl, or a fly, or a toad. It is a fascinating area and one ripe for more scientific research.

In the case of the common map (Cyrestis thyodamas), if you stand back from the image and squint your eyes (!), it is possible to imagine that the upside down butterfly does look like a moth (below). The dark black marking, and the small black tails, look a bit like legs. The effect is even more convincing on Alex Wild’s original blog. There are lots of pictures of (Cyrestis thyodamas) on this website, Butterflies of India.

 

The common map (Cyrestis thyodamas). Looking like a moth?

Personally, I think that the irregular, crisscross patterns give the impression of large fly wings. I have shaded out the surrounding areas to highlight these patterns (below).

The common map (Cyrestis thyodamas). Areas shaded out to highlight the impression of fly-like wings

I hope readers will have found these ideas interesting. I am not entirely sure whether this butterfly is trying to look like a moth or a fly, but something is going on. I believe that these patterns have a function and that they have been selected by evolution. Whether that function is to fool, deceive or mesmerise predators is not easy to say, but it has nevertheless created something of great beauty, for us at least. For the butterfly, it is a matter of life and death in the struggle between predator and prey.

Pied fantail (Rhipidura javanica) with lepidopteran prey item
  1. http://www.myrmecos.net/2013/06/25/up-is-down-down-is-up-and-moths-are-butterflies/
  2. https://whyevolutionistrue.wordpress.com/2013/06/26/yet-another-marvelous-case-of-camouflage/
  3. Quicke, D. L. (2017). Mimicry, Crypsis, Masquerade and Other Adaptive Resemblances. John Wiley & Sons.

rcannon992 View All

I am a retired entomologist with a background in quarantine pests and invasive invertebrates. I studied zoology at Imperial College (University of London) and did a PhD on the population dynamics of a cereal aphid (Metopolophium dirhodum) in the UK. I spent 5 years with the British Antarctic Survey studing cold hardiness of Antarctic invertebates and 17 years with the Food and Environment Research Agency. My main interests now are natural history, photography, painting and bird watching.

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