Adventures Among Ants - Mark W. Moffett [12]
After a time, Raja tired of the ant bites and stayed home to practice his guitar. By then I had been in Sullia three weeks, surviving on sticky rice splashed with a red curry so spicy that it often left me panting. This diet kept me ravenous, and to sustain my energy I purchased caramels at a roadside stand. (The shop had more ambition than inventory, with the former evidenced by its name, Friendly Mega Supermarket Store, which was crudely painted on a board.) I surreptitiously devoured the candy at night, fearful of hurting my host family’s feelings, and disposed of the paper wrappers down rodent burrows on the plantation.
One cool evening as I watched marauders rushing in the tree litter, as greedy for high-calorie food as I was, a vision of the ants as a superorganismic being crystallized in my mind. I began to think about the army ant stratagem of foraging in a “group.” Within the superorganism, what does membership in such a group entail for an ant? Is it proximity? Among humans, techniques as old as jungle drums and as new as Twitter allow people to form groups without physical closeness. Conversely, being close to others does not automatically confer membership in a group in a meaningful way. Often enough I have joined a crush of people on a city street—quite a crowd, but not much of a group.
I had seen many ant species in which nearby workers show no semblance of joint action. Is proximity even less meaningful to ants than to people? In many ways, yes. The workers of most ant species cannot detect another ant’s presence until they are virtually on top of each other. Army ants, legally blind by human standards, sense a nestmate only during fleeting moments of contact. In such times, the ants distinguish friend from foe, but what they learn is unlikely to play a role in the organization of their armies. Rather than responding directly to others, ants tend to react to information left by nestmates who may be long gone—to the webwork of social signals, such as pheromones, spread throughout the environment in an ant version of the Internet.
Think of household ants following an odor trail to a cookie left on a kitchen counter. What happens if I pluck out all but one ant? Her actions won’t change an iota as long as she can track the scent. She continues to participate in a group effort to harvest food whether the trail is thick with ants or not. Could we define an ant as being part of a group when her actions are constrained or guided by the varied signals and cues arising from the actions of her nestmates, and as solitary when she acts on her own?15
As it turns out, army ants conform to this view of a group. The workers have negligible freedom to wander far from nestmates and any fresh chemical communiqués those nestmates have left behind; the superorganism never sends out lone pieces of itself, but droves of workers operate as an almost tangible appendage that stays attached, through a continuous flow of ants, to the main body. Some scientists point to other aspects of army ant life, such as their ability to catch or retrieve prey in groups, but it is this aspect of their behavior—how they forage, and not what they do after they find food—that sets army ants apart from other ants.
My goal became to determine whether the marauder ant uses the army ant group approach to hunting. In India, I documented the movements of teeming battalions, with the workers numbering in the tens of thousands. But such details as whether the raids relied on scouts were difficult to assess during the bone-dry weather I experienced there, which forced the ants to be cryptic and subterranean. I would continue my marauder ant studies in Southeast Asia, where the species was common.
Rajaram Dengodi, smiling dreamily as he strummed his guitar, saw me off on the bus to Bangalore. As I climbed the steps, the proprietor