I love mimicry, for it shows very graphically the power of natural selection, and is one of the few cases in which we can judge how close natural selection can take an animal or plant toward its “optimum”—which is presumably to resemble as closely as possible the creature it’s mimicking. These examples of ant-mimicking arthropods were taken by the inimitable myrmecologist and photographer Alex Wild; they’re part of a collection of 24 ant-mimics you can see here. You can also buy prints of these, and do keep an eye on Alex’s great website Myrmecos.
Non-ant arthropods mimic ants for a variety of reasons, including hiding from predators by looking like part of an ant swarm, deterring predators by resembling toxic ants that predators have learned to avoid, and preying on ants by sneaking up on them by resembling a member of their species. Alex has examples of all three forms.
The captions below each photo are also Alex’s.
First, a spider mimicking a toxic ant (note that it has 7 and not six legs; the eighth was apparently lost) to avoid predation. Remember, this is a spider, for crying out loud!
The delicate build and sabre-like pedipalps of this Brazilian corinnid spider help it to mimic the painfully-stinging trap-jaw ants of the genus Odontomachus. Morretes, Paraná, Brazil
This is one of the more amazing mimics I’ve seen:
Heteronotus tree hoppers have a fake “ant” on their backs, presumably to foil predators.
Maquipucuna Cloud Forest Reserve, Pichincha, Ecuador
A spider (left) mimicking an ant on which it preys. Note the fake “eyespot” on the spider’s abdomen, presumably so it looks like an ant from either end:
The tropical Australian crab spider Amyciaea albomaculata mimics its prey, the green tree ant Oecophylla smaragdina.
Cape Tribulation, Queensland, Australia
Another case of “Batesian mimicry,” in which an edible prey item (the spider) evolves to mimic a toxic “model” (the stinging ant) because birds learn to avoid anything that looks like an ant. Note that this looks nothing like what you think of as a spider. Note, too, the forward placement of the first pair of legs to resemble antennae.
The spider Sphecotypus niger is an astonishingly accurate mimic of Pachycondyla villosa, both in form and in movement. The resemblance presumably protects the spider from predators, as its ant model has an extraordinarily painful sting. Jatun Sacha reserve, Napo, Ecuador
Jumping spiders often mimic ants on which (I think) they prey. Here’s a remarkable resemblance showing how far an animal can be modified by natural selection.
A jumping spider (top) mimics the common twig ant Tetraponera mocquerysi. Uganda
Finally, a crab spider (on the left) mimicking the ant on which it is nomming. This shows that ants can clearly see other insects, and discriminate against those that look “wrong.”
An ant-mimic spider (Aphantochilus rogersi) has caught a Cephalotes atratus turtle ant. Archidona, Napo, Ecuador
32 Comments
This is a fantastic read! Fascinating. Nature never ceases to amaze me.
This article by Shingleton & Frankino may be of interest New perspectives on the evolution of exaggerated traits
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http://onlinelibrary.wiley.com/doi/10.1002/bies.201200139/full#bib16
awesome.
In the last picture, isn’t the spider on the left? Looks like perhaps it has lost one of its legs.
Could be; maybe Alex can weigh in. It was hard for me to tell.
Yes- that’s the crab spider on the left, and the ant on the right. The spider is feeding from the back of the ant’s neck.
I’ll fix it–thanks, Alex!
Good way to tell: the spider has a patella and its tarsus is completely different from the ant’s.
I think you can see the typical lower leg morphology of an ant on the right, and you can count 4 leg arches on the left side of the body (the far side) of the spider on the left. Remarkable mimicry.
Thanks for sharing these, Jerry. But I’m not sure I buy the “one of the few cases in which we can judge how close natural selection can take an animal or plant toward its “optimum’” bit. Sometimes, the optimum will fall short of perfect mimicry. See, for example:
http://beheco.oxfordjournals.org/content/13/6/821.full
And also:
http://www.jstor.org/discover/10.1086/660287?uid=3739256&uid=2&uid=4&sid=21101769653143
I didn’t mean that the optimum is always attained, merely that mimicry is one of those cases in which we can get an idea of how close to an optimum natural selection can take a beast. In some cases it’s much closer than I would have thought. Sex ratio is another example, which is often very close to 50:50.
I think there are two related points here.
The first is whether “optimal” implies “perfect”. Clearly it doesn’t: mimicry doesn’t have to be perfect; it just has to be good enough to fool the target species.
The second point is that we are not that species. So in general we’re not in a position to judge whether mimicry is optimal or not. Our judgment is not the right metric.
So it’s not just a question of how close natural selection can get to optimal. It’s also a question of whether we can know how close it got.
Very entertaining read.
Very cool. Wonderful photos Alex!
And as a further indication of why it’s natural selection at work – you don’t get ants imitating spiders. Why would they? (I am aware that there will probably turn out to be at least one example where they so! This is biology after all)
Nitpick: only one of them (the tree hopper) is actually an insect.
You’re right of course: arthropods! I’ve fixed it, thanks.
Simply beautiful and utterly fascinating.
Does it (often) happen that an ant-mimicking spider mistakes another ant-mimicking spider for the ant it is mimicking?
Interesting thought!
My guess is probably not. Remember that the spiders also have to find mates of the right species, and probably have highly specific recognition signals for that purpose. Predators (or prey) aren’t likely to notice those signals, but to the spiders they’d be obvious.
But the conflict between predators and prey is one of the drivers of natural selection. The ability of the predators and prey to notice any differences is crucial to their survival. Any highly specific recognition should be possible to evolve in the adversary even if it hasn’t yet. However, if the recognition somehow required something like all eight eyes to notice any difference, that could workout fairly well but, that type of specialization wouldn’t necessarily be easily available to all mimics or originals though. It would be interesting to find out what is happening and determine if the adversary is restricted by its genetic structure from developing a detection method.
Nature doin’ its’ thing. Beautiful
“This shows that ants can clearly see other insects, and discriminate against those that look “wrong.””
Actually it doesn’t show this, but it is distinct possibility. Cephalotes atratus is a large, hard-bodied ant with sharp spines: not at all good food for birds and lizards. Also, they form large colonies, are gregarious, and, in my experience, not especially wary. A big, juicy spider like Aphantochilus hanging out near the ants (where birds can shop for the least ant-like victim) might benefit from deceiving predators. Spider appearance can be altered by painting or talc-ing. Experiments with altered spiders might reveal if ants can detect and avoid poor mimics and if predators pick them out, and off.
I agree. My first hypothesis would be that even for spiders that prey on ants, predator avoidance is the main reason for mimicry. There are plenty of ant-associates that look nothing like ants, but manage to get by because they smell OK. And, when avoiding predators, looking like an ant in the presence of “other” ants would seem to be better than in their absence, in a “where’s Waldo” sort of way.
I was wondering about the green ant mimic, is it green because ants have colour vision and would be discovered by the ants if it didn’t look like them? Or because its predators, birds, have colour vision and it’s trying to look green like the ants, or green like the leaves. I assume the ants are green to mimic the leaves of the plants they live on. This may mean we have ants coloured green to mimic leaves,(camouflage) and spiders coloured green to mimic both! It’s all very incestuous.
Green tree ants are one of the weaver ants that build nests out of leaves glued together with silk produced by the larvae. They’re bold diurnal hunters in the trees but probably do get eaten by birds; they make a tasty and refreshing vinegary snack for people too, and are widely used in Asian cuisine.
When I was living in Townsville they were constantly building nests in our front yard, and where trees brushed against the eaves there’d be a stream of ants onto the walls of the house, and finding their way inside. So I was up on the roof doing a bit of pruning, trying to be quick (they bite but don’t sting), when in amongst a mob of ants there was this one ‘ant’ many times as big as it should have been: there are distinct minor and major castes, but this one seemed to be as big as my thumb. Sadly, I didn’t have time for a good look because of an involuntary recoil, but on later inspection of the afterimage seared into my optic lobes, it had the exact colour of the ant but the face of a jumping spider. So not really mimicking the ant morphologically, but in the context enough to make me let go of the branch. Maybe Mopsus, though it doesn’t seem to be a known associate of Oecophylla. Is there another giant green salticid that does hang out with these ants, does anyone know? Or is it more likely I was deceived by the back end of an Amyciaea?
Immitation is the sincerest form of flattery…
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Or even, imitation … *sigh*
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For any one of these examples, it would be very interesting to see what incremental steps were taken by evolution over time to produce such magnificent mimicry.
Look! I Got me a leg which looks like an ant antenna! Woo hoo! Goin’ to the ant mixer tonight to chow down!
(Probably didn’t happen like that…)
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