Adventures Among Ants - Mark W. Moffett [20]
Recruitment signals come and go as food is harvested. The ever-present exploratory trails are the glue that binds individuals into a foraging group, the closest parallel in ant societies to the adhesives that join the cells of our bodies. The front-line workers’ pheromonal scents keep the foragers immediately behind them close together and moving ahead as a unit, all the while leading the raid forward.
For both the marauder ant and army ants, the varied attributes of the raids—the cohesive advance, the lack of a target other than the general land ahead, the absence of scouts—seem unrelated. But these features are manifested in a simple series of actions so circumspect and tentative that in humans they might be equated with separation anxiety. Unless they are diverted to kill prey en route, the ants are committed to a single goal: to follow fresh trails leading ultimately to unexplored terrain. Each ant stays near her sisters on routes that draw her inexorably out from the nest and onward, eventually bringing her to the raid front. There, she encounters the first land that is barren of signals. In response she runs ahead, drumming the unmarked ground with her antennae and depositing a smear of pheromone that guides those behind her. She then returns hastily to her “comfort zone” within the pheromone-saturated land behind. Such timidity is crucial to keeping the troops functioning as a unit, the equivalent of human boot-camp training. It vividly contrasts with the pluck the same worker shows when she joins the wanton melee around prey.
In the marauder ant, as in army ants, every worker is in effect shackled to a nexus of social signals generated largely by individuals who happen to be nearby. Thus it is not so much the proximity of individuals but their lack of autonomy that makes the army and marauder ant superorganisms nonpareil. No matter how much individuality may be prized, there may be times when, for a society—ant or human—to function productively, it pays to march in lockstep.
OTHER ANIMALS THAT HUNT IN GROUPS
There are other members of the animal kingdom that mass forage. Some spiders are sit-andwait socialists who weave a communal web. The more spiders, the larger the catch, with dozens bearing down to secure, say, a large moth.15 Harris’s hawks of New Mexico hunt in families of up to five, leapfrogging between perches until they see a rabbit. Then they converge for a simultaneous kill or attack it in relay. If the quarry finds cover, one or two hawks flush it out while others wait in ambush.16 Among mammals, lions, wild dogs, wolves, and killer whales also hunt in groups, staying in range of one another while seeking prey too large or agile for them to catch unassisted. Some bacteria move in similarly voracious swarms called wolf packs, with pioneers advancing and retreating in army ant style.17 By secreting enzymes together, they can digest prey far larger than a lone bacterium would have any chance of killing.18
Species that bring down large prey are not the only ones that forage as a group. Many bird species can mix together in a flock that, according to Ed Wilson, “behaves like a giant mower, leaving a pattern of well-trimmed areas juxtaposed to relatively untouched areas.”19 While birds act separately to glean