If you’re a regular, you know that all the biologists who post here love mimicry. I’ve tried to explain why: it shows the power of natural selection and the degree of perfection that natural selection can attain (i.e., how closely something can come to mimic the background or another animal—the “target”), and the very remarkable and unpredictable ways that evolution can go. But one of the main reasons is simple aesthetics: it’s remarkable to see how natural selection, sculpting an animal or plant gene by gene, can get it to look like something it’s not. Animals can look like plants, like other animals, or the background; and plants can look like plants (seed morphology mimics in weeds), rocks (Lithops) or animals (bee-mimicking orchids). And so when we see nice cases, we put them up here
Here’s a particularly nice one brought to my attention by Matthew Cobb and Erica McAlister. As described in some detail in a paper in the Journal of Arachnology (reference below; access free) and a National Geographic piece by Carrie Arnold, it’s an orb-spider from Yunnan, China that’s probably a new species. We’ve seen spiders mimic all sorts of things (including snake heads), but here’s one that apparently mimics a leaf. It is in fact the first observation of a spider mimicking a leaf.
Here’s the undescribed spider that, say the authors, is probably found in rainforests throughout SE Asia judging from photographs taken by others. The authors found only one female and one juvenile in two weeks of searching, so it’s not common (or else it’s a hell of a mimic!).
Notice the weird body shape and the tapered abdomen (the photos, from the National Geographic site, are all by Matjaz Kuntner, the paper’s first author).
As the paper reports, and as you can see above and below, the females are green and brown, and their abdomen looks like a pedicel (a stalk bearing a flower). The spider further mimics leaves by pulling dead leaves into its web alongside the live ones it uses to anchor its web. And those dead leaves have to be hauled up to the web from the forest floor!
When the web is disturbed (below), the female moves higher up her twig to mingle with the leaves. Note how she draws her legs in to hide the appendages:
The selection pressures producing this mimicry probably involve either hiding from predators or hiding from prey—or both.
As you see from the title below, the paper calls this a case of “leaf masquerade,” which they define as “avoiding predation by being misidentified.” They distinguish this from “crypsis”, which they define as “blending in with background not to be detected at all.” I find this distinction not that interesting, as both cases involve mimicry of the background. To differentiate masquerade from crypsis one would have to know whether the predator (or prey) actually notices the leaf-mimicking spider. That would be very hard to do, and, at any rate, the selective pressures operating in both cases seem identical.
Matthew also sent me a tw**t by Matt Simon, which shows all the color pictures in the paper.
h/t: Matthew Cobb, Erica McAlister
Kuntner, M., M. Gregoric, R-C. Cheng, and D. Li, 2016. Leaf masquerade in an orb web spider. J. Arachnology 44:397-400.