Why Evolution is True is a blog written by Jerry Coyne, centered on evolution and biology but also dealing with diverse topics like politics, culture, and cats.
As I’m occupied today, there will be one wildlife photo, and it’ll be a “spot the. . . ” picture. It comes from reader Siegfried Gust, who sent other photos that I’ll include in the reveal. For now, spot the katydid, As Siegfried notes:
Greetings from Costa Rica.
I came across a lichen mimicking katydid the other day and thought that you might be able to use some pictures of it on your site. Here is a wide shot that shows just how well they blend in for one of your “Spot the _______” posts.
Can you spot it? (Click to enlarge.) I consider this one “hard”. The reveal is at 1 p.m. Chicago time:
We have only two photos today, both from Lou Jost, who’s been busy in the rain forests of Ecuador. But they’re great pictures, and one apparently shows a form of mimicry new to me: an insect mimicking a frog. Lou sent this yesterday:
In honor of your mimicry post today, here are two more mimics for your delectation, found this month during a visit by a group of Stanford University students. The first is a crab spider that imitates a frog! It was found by students Dylan Moore and Natalia Espinoza in EcoMimga’s Rio Zunac Reserve.
At first they [Moore and Espinoza] thought it was a frog. It holds its forelegs in a position reminiscent of the hind legs of a frog, and its abdomen mimics a frog head, complete with eyes. I imagine that small birds or insects that would catch a spider might not want to waste energy or risk their lives trying to catch a frog.This spider seems to be related to the famous “bird poop spiders” but I don’t really know. If an arachnologist reads this, perhaps he or she could add some information about this?
The next day,when we went to EcoMinga’s Rio Anzu Reserve, I spotted this leaf-mimic katydid only because it moved its two antennae together to act more like an inanimate leaf. It was confident in its disguise and did not move when disturbed.
You do see it, right?
The frog mimic a frog raised two questions, which I sent to Lou. Is this the first described case of a spider mimicking a frog? And what could be a selective advantage to the spider of this kind of mimicry? Lou responded:
Jerry, I hadn’t ever heard of a frog-mimic spider like this, but the internet does reveal one other alleged example here [JAC: here’s the photo at the link]:
But I think that one might be imitating a snake head.
As to why a spider might mimic a frog, I don’t really know. Maybe insects that would eat spiders might be afraid of frogs? Or maybe birds that would eat spiders are not going to bother to chase a frog, which is more agile and which might be toxic?
It’s unlikely that the imitation is to help the spider sneak up on prey, as it seems that most prey that would be eaten by a spider would also be eaten by a frog. Also, the spider’s color is not an “aposematic” warning color, which most toxic frogs have, like this one:
Oophaga pumilio, the “strawberry poison dart frog”. It’s extremely variable in color and pattern; this one is the “blue jeans” morph.
That, I think, rules out the toxicity hypothesis, though not the agility hypothesis.
The first tw**t (I added others when I saw where this came from) is from naturalist and photographer Gil Wizen, who, like me, is a fan of mimicry. He’s given me permission to reproduce some of his stories and photos (like this amazing account of sexually-selected flies), and I’ll soon get around to that. In the meantime, he’s been posting mimicry photos on his Twitter page as well as photos for National Moth Week, and here’s a good one showing a mimic and a moth in one creature:
As usual, Matthew Cobb is the fount of all animal tw**ts. Here are two good ones: chicks of what I guess to be the European golden plover, Pluvialis apricaria.
I needn’t explain why I’m so fascinated with the phenomenon of animal and plant mimicry, so let us just marvel at two examples this Sunday morning as we worship at the church of Our Lady of Perpetual Naturalism.
Both were found by Matthew Cobb, and both were retweeted by Gil Wizen from the same source, which is written in Japanese. The first is a leaf-mimicking moth. Can you spot which one is the moth?
I have a soft spot for moths that take crypsis to the next level. Uropyia meticulodina masquerading as a dried leaf. https://t.co/sx3CXFEmjY
The species is found in China and Taiwan, and looks like this when pinned. Look at the markings of the forewings:
Here’s a video showing the stunning mimicry; its wings are not curled but give the illusion of it. It’s remarkable!
And a behavioral adaptation to facilitate hiding. Several insects repeatedly turn around when moving, like this one. Can you guess why? Put your guesses below, and then see the answer here.
This magnificent hemipteran is a species of Ancyra, mimicking a weevil. Look at it changing directions as it walks to increase the deception https://t.co/psRpr1zbbH
I talk a lot about mimicry on this site, and I’ve explained why: it’s good evidence for natural selection, poses testable hypotheses, and, not least, provides some amazing examples of the power of natural selection—especially because in many cases of mimicry we can identify the “target of selection”: the optimum phenotype that provides the greatest fitness. And these cases often show that the target is pretty well hit: see many examples here.
Here’s a pretty amazing one I didn’t know about, but was spotted by Matthew Cobb on Twi**er. It’s a cuttlefish that mimics a hermit crab. Or at least that’s what it seems to be doing.
Here’s a longer video from National Geographic, clearly showing that the cuttlefish mimics the crab’s shell, its antennae, and its claws. The last minute of this 2-minute video offers the hypotheses (camouflage from prey or prdators) and the situations in which the mollusks do this. But is it learned or in the genes? The video doesn’t tell us.
It’s the Pharaoh Cuttlefish, Sepia pharonis. Wikipedia explains how they change color:
Pharaoh cuttlefish often show a solid color when resting on a solid color background, alternating from a pale white to all dark brown. Additionally, they can show a mottled white and brown color, with a center circle of brown. The mechanism for color is the same in the Pharaoh cuttlefish as it is in other cuttlefish. This colour-changing function is produced by groups of red, yellow, brown, and black pigmentedchromatophores above a layer of reflective blue and green tinted iridophores and leucophores, with up to 200 of these specialized pigment cells per square millimeter. These sacs of color are controlled by rings of muscle around the sac. The cuttlefish expands and contracts these muscle rings in order to show different colors.
