The panoply of mimetic plants and animals in nature is endless, and scientists are always discovering more cases. A really cool one is described in two papers cited below, summarized by Morgan Jackson in his Biodiversity in Focus website, from which I’ve taken the pictures (they’re from the second paper cited below, one that I cannot access).
I have read the Hespenheide paper, which you can dowload for free, and it describes a group of diverse Neotropical beetles with an unusual pattern: their head and front part of the thorax is red, the rest of the thorax is black, often marked with white to yellowish stripes, and the tips of the “elytras” (hardened wing covers) are golden yellow to pale gray. Hespenheide describes at least 60 species of beetles in five families that have this pattern. Here’s one example from the Vannin and Guerra paper, which I’ve taken from Jackson’s post that describes this single species:
Here’s a shot of the species in the wild; as the Hespenheide paper points out, these beetles (like their presumed models, which we’ll get to in a second) tend to sit on tree trunks. These are all beetles:
Looks like a fly, doesn’t it? And both papers suggest that this is the evolutionary force that gave rise to the beetle pattern: it’s mimicking a fly: a sarcophagid flesh-fly for the beetle shown above. Here’s a picture of a sarcophagid fly:
The mimicry’s pretty good, isn’t it?
Now there are several reasons for this mimicry. The fly, for example, could be distasteful or poisonous, and birds could learn to avoid its pattern. A tasty beetle, by evolving to resemble that pattern, could enjoy some protection from sharp-sighted bird predators that have learned to recognize and avoid it. That’s called Batesian mimicry. Alternatively, both beetles and flies could be distasteful/dangerous, and evolve to resemble each other because having a common pattern facilitates predator learning, conferring extra protection. That’s called Müllerian mimicry. Neither of these seem applicable in this case because flies simply aren’t distasteful to predators (mostly birds).
Both authors, however, suggest a different explanation—actually a variant of Batesian mimicry. The likely solution is that flies are simply hard to catch for birds—even entomologists with big nets have trouble nabbing flies (ask me!). Studies show that flies are rare in bird stomachs compared to other potential prey. Both authors, then, suggest that bird predators simply learn to avoid going after flies because they’re hard to catch, and the reward is unlikely to match the futile effort. Once a bird has learned to avoid catching flies, then any beetle (mimic) that looks like a fly (the model) would also be avoided. That’s the selective pressure on the beetle to accumulate mutations that make it resemble the model.
Now this could be tested: one could expose a naive bird to flies, watch it go after them, fail miserably, and then expose the bird to the mimicking beetles. It would presumably then avoid the beetles. However, birds that hadn’t been exposed to flies, and thus hadn’t experienced dipteran-related failure, would go after the beetles more readily. These kinds of tests have been done with other kinds of mimicry, and succeeded remarkably well. They haven’t, however, been done with these insects.
Nevertheless, the explanation is a good one, for the mimicry is so obvious, and it’s just another marvel that we lucky evolutionists get to read about every day.
If you’re a strict creationist, you should ask yourself why God would make a beetle look just like a fly. One could always answer, I suppose, that it pleased God to do so, or that His ways are mysterious. But that’s the end of the questioning. The evolutionary hypothesis leads to predictions, including the experiment I suggested above. Another is that beetles that mimic flies should live in the same areas that flies do, and encounter the same potential predators. That’s not a necessary prediction of the God Hypothesis.
Hespenheide, H. A. (1973). A novel mimicry complex: beetles and flies, Journal of Entomology Series A, General Entomology, 48 (1) 55. DOI: 10.1111/j.1365-3032.1973.tb00034.x
Vanin, S.A., & Guerra, T.J. (2012). A remarkable new species of flesh-fly mimicking weevil (Coleoptera: Curculionidae: Conoderinae) from Southeastern Brazil Zootaxa, 3413, 55-63. PDF Available Here