by Francesco Lami
Camouflage is a widely adopted trick by organisms, especially animals, to avoid predators or surprise preys. Awesome myrmecologist (what’s with this blog and myrmecologists, anyway?) Alex Wild of Myrmecos fame has posted some days ago an article about what might indeed be one of the most incredibly elaborated camouflage tricks in the already incredibly elaborated world of camouflage. Click the link and look at that goddamn moth, Macrocilix maia: as Alex himself pointed out, it’s a whole mural, depicting two red-eyed flies feeding on bird droppings, complete with light glinting off the wings and the poo. Especially if looked from a few feet of distance, those really look like real flies and real crap, probably realistic enough to trick a bird anyway, and to make the whole thing more convincing, the moth smells bad (what’s with this blog and smelly animals, anyway?). I must admit, however, that I’m a little bit skeptic, and I’m not even the first one, to feel that way. Matthew Cobb wrote a post at Jerry Coyne’s WEIT addressing the most important problem with the theory: ok, flies makes the whole “bird shit” scenario a lot more realistic, but wouldn’t they attract fly-eating predators? While I still think that this, while a good objection, might not be enough to completely destroy a theory supported by the fact that the moth not only does look like bird droppings with flies, but also stinks like bird droppings with flies, I can’t help but think that this might just us seeing things we imagine where there are none, not differently from a Rorscharch test. It’s a story similar to that of the Samurai Crabs, whose face-like carapace has been suggested by some to have been artificially selected by superstitious japanese fishermen who released all the crabs which remotely looked like human faces, while others think it’s just a case of paraeidolia.
Long story short, the question is: do the wings of M. maia look like bird shit thanks tnatural selection, which gave the advantage of not being eaten to the shittiest moths? Or is that just one of the many varieties of moth wings, in which we have seen what we wanted to see (which is… shit, I guess)?
The Cladogram 
Francesco, as I mentioned on Jerry’s site, I think these patterns might represent beetles rather than flies. Note the reflection at the top of what would be the carapace. The squared-off middle segment also looks more beetle-like than fly-like. And unlike flies, many beetles are distasteful and spray nasty chemicals. So it is easy to imagine natural selection favoring this pattern (whereas I can’t imagine why insectivorous birds would avoid flies). Of course this isn’t proof, but it is something which could be tested. For example, if my hypothesis is correct, there should be distasteful or (better) noxious beetles in that habitat with a red and black pattern. If there are not, my idea falls.
People are afraid of just-so stories, but this leads to the opposite extreme of intellectual cowardice. Lots of these things do have reasons (though some are random), and often our visual system and brain are enough like those of important predators that we can make good guesses about the function of color patterns on prey. And these guesses are often falsifiable. Here is an example from plants—caladiums in Ecuador often have white squiggly lines on their leaves. Somebody noticed that these lines looked like leaf miner tunnels, and hypothesized that leaf miners would prefer to lay eggs on leaves that were not extensively eaten already. Thus, fake damage would repel leaf miners looking to lay eggs (much like the fake yellow eggs produced by some Passiflora vines ward off ovipositing Heliconius butterflies). Sure enough, an experiment with artificially painted Caladium leaves showed significantly less leaf miner damage on painted leaves than on green leaves.
So I think we should be brave and imaginative and use our brains to try to figure out the whys of these kinds of patterns, and make testable predictions from them.
That’s a really good point Lou – and the hunt for the distasteful beetle/fly/thing is officially open! I actually wasn’t trying to say that the camouflage hypothesis for that moth was certainly wrong, as I know there are so many amazing tricksters in nature. It’s just that this one seems almost too awesome to be real – but as we know, reality is often stranger than we could ever imagine.