One of these things is not like the others

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Cephalotes pusillus is ever-present in cerrado. In fact, I have never encountered another ant that is so abundant in a natural system, tropical or temperate. They are generalist nesters and can be found in almost every piece of standing dead-wood and many live trees. The workers are particularly robust, even for Cephalotes, and will often bulldoze their way to foods already overwhelmed by other ants.

C. pusillus worker

But even for these tank-like ants, trouble lurks in a surprisingly familiar form. The aphantochilid spider Aphanlochilus rogersi is a very striking mimic of C. pusillus, but not for the purposes of protection. It is an infiltration tactic. A spider will sit on the edge of a foraging trail of its model, seemingly undetected by the ants. When one worker strays too far off the beaten track, the spider strikes and runs with its prey before the large and dangerous foraging force has time to react. These spiders are remarkably abundant…but very fast. It took me a good year to get this shot of one of these hunting mimics with its prey and model.

lunch
The ant-mimicking Aphanlochilus rogersi with a paralyzed worker of its model, Cephalotes pusillus. This shot is on the underside of a branch. The foraging column from which the C. pusillus worker was plucked was on the upper surface.

For those wanting to read more, there is a nice older paper on this interaction (Oliveira, P.S. & Sazima, I. 1984. The adaptive bases of ant-mimicry in a neotropical aphantochilid spider (Araneae: Aphantochilidae). Biol. J. Linnean Soc. 22: 145-155.)

5 thoughts on “One of these things is not like the others”

  1. Aydin, you might be right, but the spiders are even sneakier than I let on. They often hold their front legs out in front of them, mimicking the ants’ antennae. This is quite a common behavior in ant-mimicking spiders.

  2. Is it my impression or all ants in the cerrado are built up like a a tank. Many of them have this sturdy, buffed up aspect. Why?
    In fact, why some ants are so armored like Cephalotes and why some are so slim and slender like Oecophyla?

    1. Beto, I don’t think cerrado ants are especially well armored compared to the same species, or the same lineages in other tropical locations. Cephalotes is a lineage where armor is an ancestral defense for a sneaky foraging ecology, where attacks from large-colony aggressive ants are common. In contrast, Azteca are as flimsy in the cerrado as they are everywhere. Their defenses are chemical and supported by strength in numbers. In other words, the armor (or other defenses) seen in a particular lineage result from a combination of history and ecology, but I don’t think the ecology of the cerrado exerts a general selection pressure for armor across all ant taxa. We can discuss this further in lab meeting :o)

  3. Pingback: The Ant that Wasn’t (Aphantochilus rogersi) – MYRMECOS - Insect Photography - Insect Pictures

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