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.
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.
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.)