Adventures Among Ants - Mark W. Moffett [35]
Marauder colonies maintain a fast, steady, well-protected flow of food and labor on their trails. Whereas small ant colonies, like people in small societies, are able to access and distribute the supplies they need without roads, larger groups depend on an infrastructure so complex that in the marauder ant it rivals human highway systems. The idea of a superorganism applies here, of course: whereas a microscopic organism like a microbe can rely on simple diffusion to distribute nutrients through its body, a large one, such as a human being, needs a circulatory system.1
A marauder ant major worker hefting a Diacamma ant killed after intruding on the colony’s trunk trail. The discarded corpse was buried by the minor workers.
ROADS
Marauder colonies avoid both gridlock and species confrontations, like that with the Diacamma worker, when trails are in good shape. Highway construction efforts are part of the society’s logistics, providing supply lines for fresh combatants on the front lines as well as streamlined routes for bringing home the plunder.2 Trunk trails are well looked after—that’s how they can be distinguished from the fleeting paths created by raids.
Each worker size class participates in the creation of the roadways. All the castes eliminate surface irregularities along a trunk: while the medias and majors chisel out embedded roots and pebbles, minor workers extract grains of soil, establishing the road’s slightly concave shape in cross section. The dross is discarded along the edges of the trail, where it accumulates in embankments like the one the Diacamma walked over. When the ground is moist, the minor and media workers build up the ramparts into a complete soil cover, or thin-roofed arcade, fabricated from soil extracted from the trail surface or from mining shafts—blind-ended tunnels near the trail used specifically as quarries.
Members of the construction crews expend their efforts foraging for building material rather than food. It is likely that no communiqués pass among them.3 Rather, like compulsive bricklayers unable to go by an unfinished wall, passing ants respond to the ongoing building project, and the structures emerge without any active collaboration. The portions of the walls that are suitably positioned and shaped along a trail attract the most attention from passersby bearing soil bits. As a result, the arcades rise to completion where they are most needed, without a blueprint, and damage to them later is repaired without fuss.
Accomplishing large projects without communications is called stigmergy. The marauders’ approach to building has been duplicated by robotics experts, who have discovered that it’s cheaper and easier to achieve a goal such as piling up small objects with a group of simple robots responding to the work done thus far than with one large, more intelligent robot.4 Stigmergy is at work in such websites as Wikipedia and Google as well, where many people add their insights to the statements and choices of others.5
Major workers of the marauder ant serve the role that humans reserve for heavy-duty construction equipment. I have called the largest of these individuals “giants” since the day I first saw one lumber from that nest in Sullia to the cheers of Mr. Beeramoidin and other forestry officials. Imagine a man and an elephant working together to build a road; the size difference between the giant and the minor worker is nearly ten times that great.
Relatively scarce, the giants tackle jobs that, though infrequent,