A roving band of Cerapachys larvatus. The full party contained about a dozen ants (Australian Alps, Victoria)

Those of us in the Americas who think of predatory ant-killing ants usually imagine the specialized army ants. These nearly blind insects roam in stereotypically large columns across the landscape, attacking prey colonies with forces of thousands. Army ant raids can be spectacular, enough so to raise the question of just how such an unusual behavior could have arisen from more typical ant ancestors.

Army ants didn’t evolve their mass-raiding predation instantaneously (in spite of creationist assertions otherwise). Rather, they belong to a larger group of ants, the so-called “Doryline section”, whose members exhibit a great diversity of ant-killing strategies. We can see how intermediate army ant lifestyles work from example. Hundreds of present-day species, especially in Africa, Asia, and Australia, make a living at them. Many of these older lineages have decent eyesight, stationary colonies, and raid in rather civilized small parties. Apparently a taste for ants came first, accompanied by group foraging, while the massive raids and nomadic lifestyle followed in only a subset of more recent species.

Below is a short photographic essay covering a Cerapachys larvatus raid Mrs. Myrmecos & I happened across in the Australian Alps last year. We don’t have ants quite like these here in the United States, so our chance observation of an unfolding raid was a rare treat.

Mrs. Myrmecos searches for ants along a rotting log. Our Cerapachys subjects appeared over the far end at the left, a dozen ants moving erratically along the top of the log.

The habitat: native eucalyptus forests in the Australian alps near Harrietville.

The raiding party stops to inspect a crack in the log, a potential nesting site for their prey species.

Once the raiders have discovered their target, a nest of orange Stigmacros full of tasty larvae, fighting ensues.

The Cerapachys raiders quickly surpass the Stigmacros defenses and are able to pass freely into the nest.

The Stigmacros queen escapes across the log. She was so quick to evacuate that I almost missed her. If enough workers survive the raid, her move may allow the colony to reconstitute after the raid.

A Stigmacros worker makes a run to get eggs out of the reach of the raiders.

One-on-one, the little Stigmacros workers are no match for the armored Cerapachys.

A Cerapachys emerges from the raided nest and grooms herself.

I took a worker back to the studio to grab this portrait. Note the small mite adhered to her hind leg.