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An Enemy in the Ranks

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About face: the false ant on the rear of the ant-mimic crab spider Amyciaea albomaculata.

Imagine, for a moment, the horror if we humans were stalked by a common predator that hid itself in the open by looking…just like us. A humanoid patrolling the streets like a bloodthirsty mannequin, picking off pedestrians that venture too close. Fortunately for us, this sobering thought is only a grim fantasy.

Australian weaver ants, however, routinely face just such a nightmare predator. Several species, in fact. Weaver ants (Oecophylla smaragdina) contend with a number of ant-like spiders that look similar enough to their favored food to avoid detection by the ant guards. They lurk around the ants’ trails, pretending to be ants and grabbing a meal when the opportunity arises.

During my recent travels in tropical Australia I spent a morning observing an ant-mimic crab spider Amyciaea albomaculata. The following photo essay shows the spider at work.

A weaver ant worker pauses to groom herself. Notice that her eyes are about the same size and distance apart as the eyespots on the rear of her predator.

Weaver ants make nests by binding leaves together with silk.

The spider grabs a hapless ant, injects a paralyzing venom, and drags her victim up a vine and away from the ants' busy trail.

The great getaway.

The spider finds a quiet spot away from the ants' trail to inject a slurry of digestive enzymes.

Does this spidey-face remind anyone else of a Studio Ghibli monster?

Once the venom has turned the ant's innards to soup, the spider sucks the mixture up as though it was a little ant slurpee. This photo shows an air bubble forming inside the ant's head as the spider drinks.

A male Amymyciaea I photographed near the female. During my morning's observation she appeared uninterested in his advances and chased him away. He is recognizable as a male by the bulbous sex organs near his mouth.

See also Aphantochilus rogeri, a New World crab spider that attacks turtle ants:
The Ant That Wasn’t

Alex Wild About the Author: Alex Wild is an Illinois-based entomologist who studies the evolutionary history of ants. In 2003 he founded a photography business as an aesthetic complement to his scientific work, and his natural history photographs appear in numerous museums, books, and media outlets. Follow on Twitter @myrmecos.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. Capularis 10:28 am 01/30/2012

    An exciting series. It’s great to see the behavior and habitat of the bugs rather than just portraits without context. (Although I like those as well!)

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  2. 2. Sean McCann 12:55 pm 01/30/2012

    Those are some beautiful ants and spiders! Great work!

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  3. 3. Gozde 3:20 pm 01/30/2012

    Fascinating. Thanks for sharing these beautiful photographs.

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  4. 4. TheBugGeek 5:39 pm 01/30/2012

    A-ma-zing. I love a good story in nature photographs, and this is a GREAT story, my friend!!!

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  5. 5. BrainWorld 9:07 pm 01/30/2012

    “Imagine, for a moment, the horror if we humans were stalked by a common predator that hid itself in the open by looking…just like us. A humanoid patrolling the streets like a bloodthirsty mannequin, picking off pedestrians that venture too close. Fortunately for us, this sobering thought is only a grim fantasy.”

    Not true. There are psychopaths among us, predatory monsters lacking empathy and conscience, looking like humans but missing the essential qualities that would make them so. While not every psychopath is a serial killer, every serial killer is a psychopath. But every psychopath is a predator in one way or another. To those who find themselves victims of one, they are a sheer horror beyond imagining.

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  6. 6. Diesel67 12:08 am 01/31/2012

    We are living that horror right now. The predators stalking us are known as terrorists. Their females tend to wear scary-looking outfits that cover every square millimeter of their bodies except their eyes, but their males can look like us, dress like us, walk like us and talk like us. Their hatred of normal humans is as venomous as that of any ant or spider, so venomous that they are impelled to do nasty things like fly planes into buildings and blow themselves up on crowded buses. They transmit to their young the capacity to synthesize venom with special schools funded by Saudi Arabia. They are brainwashed to believe that they are doing God’s work and will be rewarded with beautiful virgins in terrorist heaven, such brainwashing reinforcing their natural tendency toward mischief directed at normal humans. The only defense against these predators is a constant state of heightened arousal and readiness for battle, which draws resources away from other urgent needs. Since these predators can exist only by devouring normal humans, it is predicted that either they or we will go extinct in the near future.

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  7. 7. David Illig 7:57 pm 02/2/2012

    Wonderful pics and captions. Kudos to the beautiful spider, as well.

    David Illig
    Budding nature photographer, >60 still images and videos in EOL.

    Poor Diesel67! He is willfully full of venom and ignorance. He thinks that ants and spiders can hate! Has he lived in the Arab world? Does he know Arabic? Has he heard of Timothy McVeigh & Co., or the Ku Klux Klan?

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  8. 8. HBG_Dave 6:38 pm 02/4/2012


    (and I won’t say anything else, since the comments seem to have sunk as low as they could go already)

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  9. 9. dalma.boros 12:13 am 03/3/2012

    This is really fascinating. I didn’t know that ants could produce silk. Do they have different silks for different purposes, like spiders do?

    Also, the spidey-face does look quite a bit like the radish spirit from Spirited Away.

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