Nope, not an ant, but a spider.
This photo of an ant-mimicking spider came to me from Chris Buddle via Geekinquestion via Matthew Cobb. I don’t know the species, but the mimicry is remarkable: the front legs are held out in front so they resemble the antennae of an ant (spiders have 8 legs, ants 6), and the cephalothorax (the fused head and thoracic sections of a spider) has a fake constriction so it looks like the true tripartite nature of an ant (separate head, thorax, and abdomen).
There are many selective pressures that could modify a spider’s morphology like this, including fooling the ants so they accept the spider as one of their own, allowing it protection from predators as it hides among ants (birds often avoid eating ants). Such mimicry could allow the spider to travel with the ants and get access to food, as in the case of spiders that evolve to resemble army ants. It could also allow the spider to fool the ants so it can actually eat them.
I don’t know the answer here (and of course multiple selection pressures could be operating), but it is remarkable how the spider’s environment has interacted with its genes to cause such a resemblance. It also shows that whatever genetic constraints were operating in the spider, they weren’t sufficient to prevent a complete re-molding of its body.
It was Darwin’s genius to use the success of artificial selection—plant and animal breeding—as a way to convince people that natural selection could also produce such changes. That is why he starts off The Origin with a discussion of breeding in pigeons and other species. As he said, “Breeders habitually speak of an animal’s organisation as something quite plastic, which they can model almost as they please.” From there it’s not much of a stretch to see how nature (and I’m speaking shorthand here, for “nature” is not a force that operates on genes), could also do such modeling.
Et je ne suis pas une araignée!
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Ni une arachide.
Thanks for confirming that! It’s good to be clear 🙂
I always call peanuts “arachnids” because of the French for peanut. I especially like this on the labelling for peanut M&Ms. 🙂
“May contain traces of spiders”
Looks to me like the front legs are held out to mimic both the ant head and antennae. That might be a first!
I first found out about these guys from here.
Cool & terrifying – my usual feeling about spiders.
Is it supposed to say spider’s instead of ant’s?
Or do you mean the ant’s enviroment interacted with the spider’s genes?
Oops. Spider’s genes, of course. I fixed it, thanks.
All IMO, but…
That’s probably not the adaptation going on in this case. There are spiders that do that (see next paragraph), but the primary ant senses are tactile and pheromones, not vision. Many ants – even the soldiers and foragers – are effectively blind. If it looks like an ant to sharp mammalian eyes like ours, then the adaptation is probably geared towards some critter that sees about the same way we do.
There was a show on the science channel a week or two ago covering (heh) a different spider that does, in fact, have an adaptation to fool ants into letting the spider into their nest. It basically picks up a dead ant and carries it over it’s body. Same feel and smell as a live ant.
Incidentally and somewhat OT, spiders themselves have pretty bad eyesight (despite the bonus eyes). They are also fairly tactile. Evidently, tarantulas do most of their hunting by laying down a subtle blanket of silk, sensing when its disturbed within a few inches of them, and then..ambush. They don’t just chase down bugs and kill them; they can’t see that well.
Check out #5 on this site about ways to die if you’re an arthropod – the ant was betrayed by a spider mimicking an ant.
Dear professor Ceiling Cat, I’ve got a question:
I was reading a book from the 1930s recently, by a russian poet who got enraptured by natural science, and especially Neolamarckism, which was (even before Lysenko) the ruling paradigm in the UDSSR that time.
My question now is, was the debate between Darwinism and Lamarckism still open back then – Wikipedia at least claims so – or were the evidence already conclusively on side of natural selection. In other words, how would you have debated a Lamarckian back then? (My own feeling is that Batesian mimicry would have been quite a knockout argument.)
That there are a fair number of spider ant mimics in North America is shown by a BugGuide search on the term. But there is also the issue of chemical mimicry of ants. One case involves caterpillars of certain lycaenid butterflies, and there is a remarkable Attenborough video showing how this works and how evolution countered the problem that it posed for the natural enemy Ichneumon eumerus.
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Wow, this is something else!
That’s what the ant said that met the spider….just before he got nommed.
I’ve not seen cephalothorax used for spiders. I’m familiar with the terms Prosoma and Opisthosoma. I have a vague memory that the prosoma is not exactly homologous to the cephalothorax of decapod crustaceans.
Well, I googled and see the terms used as synonyms. Not in my day! Just another sign of the deterioration of Western Culture.;-)