Adventures Among Ants - Mark W. Moffett [144]
That’s only the half of it. Like the protagonist of Gogol’s story “The Nose,” we don’t expect our body parts to wander off. But a supercolony’s ability to span space and time leads to quirks in individuality like nothing described before. Not only do Argentine workers move freely between interconnected nests, but because the pilgrim ants transported by nursery trucks in California or on floating debris in Argentina produce offspring that identify with the colony they came from, they spread their nationality. By leapfrogging about, each society re-creates itself in fragments. One part of the Lake Hodges Colony, for example, thrives 50 kilometers north of Escondido, around the town of Temecula, where it is as isolated as Alaska is from the Lower 48. New Zealand is occupied by a single supercolony, which—given the commerce between New Zealand and California, where the Very Large Colony controls the port cities of Richmond, Oakland, San Francisco, Long Beach, Los Angeles, and San Diego—is very likely an offshoot of the Very Large Colony. No one has checked.
Supercolonies confound our notions about societies, populations, and species like nothing else. An Argentine ant society is separated socially and reproductively from all other Argentine ants by an intolerance of outsiders. That differs from humans, whose cultures, though often violent toward one another, have a history of interbreeding.25 Because there is almost no interbreeding between supercolonies, each effectively exists in isolation, as genetically isolated as lions are from tigers. In a very real sense, each Argentine ant society is its own species.26
Among Argentine ants, a new society (one with its own identity) may therefore be able to form only over the slow march of time. New species—“groups of interbreeding natural populations that are reproductively isolated from other such groups”—can originate as a result of the genetic differences that accumulate when a population becomes isolated from, and eventually unable to reproduce with, other populations of the original species.27 Similarly, it should be possible for a supercolony to split in two over time as an isolated part of the society changes enough that the two groups would kill each other if they came back into contact.28
Back in Escondido, I extended a finger to touch the mêlée of workers on the borderlands between Lake Hodges and the Very Large Colony. I must have broken up a fight. Immediately the translucent ants scurried over my skin, their delicate bodies causing a barely perceptible tickling sensation before they fell harmlessly onto my feet. The Argentineans are right: what a bland beast this is! As a graduate student rummaging through Harvard’s ant collection for novel morphology as a clue to fascinating behavior, I didn’t give the feeble-looking Argentine ant workers a second glance. As the police would say, they have no distinguishing marks or features—or none that anyone but an ant nut would notice.
Yet these ants and human beings are the only animals capable of forming societies that can grow without bounds.29 As a result, the Argentine ant, together with a few other invasive species and our own kind, has taken over vast tracts of the Earth. This achievement requires not individual strength but social coordination at a mass scale, made possible for the ants by their persistent group identity: a supercolony that truly lives up to the name superorganism.30
THE BATTLE OF THE SUPER ANTS
Only one thing appears to bring the Argentine ant to its tiny chitinous knees: an encounter with an invasive species more insidious than itself. This has already happened in the southeastern United States. The red imported fire ant, Solenopsis invicta, indigenous to the same floodplains of Argentina as the Argentine ant, entered North America in the 1930s via the port city of Mobile, Alabama.31 Spreading across the same broad regions of the South controlled by the first wave of Argentine ants that had arrived in New Orleans four decades before, the fire ant originally organized its