The Ant that Wasn’t (Aphantochilus rogersi)

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Aphantochilus rogersi (left) with prey

The most astounding arthropod I found in Ecuador last month wasn’t an ant, believe it or not, although it looks just like one from a few feet away.

Aphantochilus is a crab spider slightly over a centimeter long.  The species isn’t exactly uncommon in the Neotropics- in fact, Aphantochilus has appeared previously on Myrmecos. Rather, it is spectacular for its color, size, shape, texture, and movement. Aphantochilus is a convincing stand-in for Cephalotes atratus, the giant turtle ant, and every time I see one lurking about the margins of a turtle ant trail I do a double take and gleefully pass the next half hour watching it work.

Last month’s encounter was the first time I had a camera handy. Thus, some photographs to share with you folks.

A quiet moment

Although it may seem that the spider uses its impressive camouflage to fool its prey, I am not convinced.

The vision of most ants is rather rudimentary, enough that I think it unlikely such remarkable visual mimicry would yield enough of a payoff to be worthwhile. Ants perceive their environment predominately in a chemical medium. Instead, I suspect the spider intends to fool other visual predators- birds, maybe- that would normally pass up acidic chitinous ants but would happily take a spider. For more detailed explorations of the topic, see here and here.

Which is the spider, and which is the ant?

photo details
Canon EF 100mm f/2.8 macro lens & 12mm extension tube on a Canon EOS 7D
ISO 200, f/16, 1/250 sec. Indirect strobe bounced off white paper

33 thoughts on “The Ant that Wasn’t (Aphantochilus rogersi)”

  1. Amazing degree of mimicry, and I would agree that it serves to fool predators rather than their prey. I could see strong selective pressure for strong resembling the ants, as even the slightest difference could surely be detectable by keen-sighted birds.

  2. Wow. I am glad you had a camera handy.

    It’s been a while since I’ve said it, but thank you for your talent and the work you have put into your craft. I am envious beyond words–the worst part is, I know full well that it’s not my camera that is insufficient, but what’s behind it.

  3. Absolutely spectacular, Alex! What a cool critter; I had no idea there were Thomisid spiders that mimicked ants (had seen pics of Salticids). Is there any evidence for chemical mimicry by the spiders? Is there any reason for the ants to tolerate the spiders’ presence if they can detect them?

  4. Wonderful pictures!

    Although I can’t help but offer an alternative perspective on the mimciry. The idea that ants don’t have great vision might be true generally, but Cephalotes have amazing vision. All the better to identify potential threats so that they can engage their impressive array of non-agressive defenses (e.g. folding in appendages to leave only an armored shell, sliding under bark, jumping and gliding, etc.). If this predator looked less like an ant, I would guarantee that the target Cephalotes would initiate some defensive response before it even got close, reducing success. I have seen a number of Cephalotes species identify and avoid non-mimetic spiders. The fun thing is that these ideas are testable for someone willing to go looking for a lot of these spiders.

    In terms of the payoff (driving this kind of excellent mimicry), it could actually be pretty high. If you can tap into a diverse, locally abundant, non-agressive and non-chemically defended group of ants as prey, you are hitting the big-time. That is exactly what Cephalotes is in the canopy. The mimicry allows them to overcome the defenses that otherwise make Cephalotes a hard target.

    1. Oh, those are fightin’ words, Scott!

      You’ve spent a fair bit more time watching these animals than I have, though, so I’m happy to defer to your opinion. An excellent suggestion for a student project.

      1. Possible cases of aggressive mimicry are always hard to sell, but I do think this is a strong candidate and worthy of a solid test. Now to find that student…

        PS. I can’t wait for army ant week. I’ll try my hardest not to start any fights 🙂

  5. Woahhh, love this!
    I saw an ant-mimic spider in Ecuador, but I wasn’t able to get a photo before it disappeared. Still kicking myself over that one, really wanted to know what it was.

    1. That’s exactly my experience with the spider mimics, too. These photos were attempt #4 with this species during the Ecuador trip. Fortunately, it was the one time I caught one with prey.

  6. Spectacular pics! But why is C. atratus so different from other Cephalotes? Only C. alfari seems to be as spiny and long-legged as C. atratus, and all the others seem to fit the name ‘turtle ant’ better than these two.

  7. Wow, truly amazing mimicry there. Took me a while to figure out which was prey and which predator in image #1. Love image #2!

    These Aphantochilus surely do a good mimicking job. Way better than the weaver-ant-mimic crab spider – Amyciaea lineatipes(?) I see here.

  8. Thanks for the great shots !

    It’s hard to make out….Does the spider have the ant by the head-neck intersegmental membrane?

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