who was now deep within the swarm. Here the media and major workers roamed in numbers (click). The large ants were as plucky as the minors, and they had the size and mandibular power to be worthy of the designation “soldier”; but by dint of their location, most of them joined the fray at the termite only after the prey was felled (click).
My images transferred onto a storyboard that showed that inside the raid, after the minor workers immobilized the body, the medias and majors were a strike force that moved in to inflict what carnage they could. Small media workers fit into tighter nooks and crannies than the majors can reach, perhaps yielding a kind of division of labor in destruction.
The allocation of effort between the minors, which restrain prey, and the medias and majors, which smash it, is related to their respective locations within the phalanx. It’s unlikely that special communications are used to get ants to these positions; instead, the minors reach the front lines first because they walk more nimbly than their larger sisters, while the larger ants are waylaid by their duty to crush prey farther back in the raid. Regardless, the role of minors at the front lines is clear. Only they and a few small medias secrete trail pheromones, testament to their importance in moving the raid ahead and summoning others to prey.
To a military historian, the marauder ant strategy evinces a classic use of personnel. Placing large numbers of abundant and expendable weak individuals in jeopardy at the front lines not only increases the catch but also minimizes the loss to the society overall. The Romans used a similar strategy at their battlefronts: instead of drawing from highly trained city dwellers, they largely conscripted farmers, who were available in droves and could be replaced at little social cost—a practice that continued at least into medieval times, when poorly trained men were, literally, used as cannon fodder.7
The minors’ bold actions assure few large warriors being sacrificed, a sensible outcome given the expense of raising majors that can weigh hundreds of times as much as one minor. In a sense, the medias and majors are equivalent to the human warrior elite—physically stronger, superior fighters, often positioned behind the relatively inefficient front-line rabble. The human elite are provided with better weapons and training and protected by the most expensive armor, as tough as a soldier ant’s exoskeleton.
The large workers are attracted to a prey’s flailing extremities and dutifully hack off every moving leg and antenna. With the prey rendered powerless, unless its shape is awkward (like that of a praying mantis, which the ants will tear apart), the minors heft its body back in one piece. I once saw the ants retrieving a limbless gecko, which clued me in that they had taken it alive.
Dismemberment immobilizes but doesn’t necessarily kill. Moving animal prey to the safety of the nest before the coup de grâce may reduce the chance of its being stolen by competitors or washed away in a storm. By keeping prey alive, the ants may also be able to preserve their meat (something that ants with stingers do by paralyzing their victims).8 I learned of this strategy one day at the Botanic Gardens when I snatched a limbless katydid from marauders on the way to their nest. I put it in a jar and forgot about it until, two days later, I noticed its leg stubs still writhing. That night I dreamed I was that katydid, being helplessly transported to the bowels of the nest, to be digested at the ants’ convenience by the protein-hungry larvae.
SPRINGTAILS
Marauder ants conduct raids to catch tough prey, but mass foraging helps them obtain other kinds of meals as well. The poorly armored minors, though not intimidating, are agile and have good vision. I’ve watched hundreds of them retrieve speck-sized jumpers called springtails.
Springtails are the rabbits of the insect world—fast breeding, abundant, and prodigiously jumpy. As the name implies, they use their tails as a spring. If one senses a threat, its tail, or furcula, normally folded under the body, snaps downward, launching the insect through the air.
Before exploring the marauder ant’s tactics for capturing these motile creatures, let’s first look at a very different approach. A speck herself, a burnished red Acanthognathus teledectus ant moves stealthily through the forest litter in Costa Rica, her long, pitchfork-shaped mandibles held straight to each side. Coming on a springtail, she slows to a glacial creep until two long hairs extending from her mandibles touch the quarry, indicating that her distance is perfect. Her jaws snap forward; their prong tips puncture the springtail and hold it tight. Quickly now, the ant slings her hind end under her body and incapacitates the prey with an injection of toxins through her sting, after which she hefts it overhead and carries it home.9
With blows from her mandibles, an Acanthognathus trapjaw worker in Costa Rica repels a pseudoscorpion from the tiny hollow twig occupied by her colony. Behind her, a larva feeds on a springtail.
Acanthognathus displays the special skills required for solitary-foraging species to snare these speed demons. Success among springtail-hunting virtuosos depends on stealth and the use of mandibles as an unusual tool. Devices such as trap jaws and stingers are especially common among species with small colonies with only one kind of worker, such as Acanthognathus, whose workers so often need to act alone. Unlike with the antlers of moose or the tusks of elephants, their function is not to impress but to kill and butcher.
“Trapjaw ants” like Acanthognathus have evolved repeatedly among lone-foraging species. Typically, their mandibles are long, with pitchfork-like teeth only at their far ends, and they can open 180 degrees or more. In many cases, the jaws come equipped with trigger hairs. While the ants can be slow, their “bear-trap” jaws are not: the fastest muscular-driven action for any animal is achieved by the jaws of one group of these ants, Odontomachus.10 These speed-biters nab insects and also ply their mandibles as defensive tools, striking them against the ground when harassed; the resulting recoil sends them flying head over heels to safety. In Surinam, I’ve seen schoolchildren, betting over candy, make a game of encouraging the Odontomachus ants’ bouncing behavior while trying to avoid their searing stings.
Long jaws are great for catching prey but impractical at mealtime. Asian Myrmoteras, another group of creeping trapjaw ants that nest in any dark corner of the leaf litter, chew their prey from afar using the spiked tips of absurdly thin mandible blades that they can open an extraordinary 280 degrees. After chewing, they walk forward to place their mouths on the victim and feed at the oozing wound, then circle back to chew some more—the most awkward and labor-intensive approach to dining I have witnessed in all my travels.11
Acanthognathus have a partial solution to this logistical problem. While they use their long jaws to seize skittish springtails, they avoid the arduous dining experience of Myrmoteras by having a face like a Swiss army knife, with an entire arsenal of utensils at their disposal. To eat, they open their jaws wide, revealing a pair of what look like normal mandibles but are actually curved teeth, sprouting near the base of the longer bear-trap blades. The workers masticate their springtail meals to a pulp with these minijaws. As the small jaws are of a piece with the rest of the mandible, chewing with them sets the bear-trap blades waving to such a degree that feeding ants often knock over their neighbors.
Marauder ants have no elaborate built-in tools with which to seize springtails. Instead they must rely on commonplace, workaday mandibles (which have several small teeth along their forward margins, as do those of most ants). Furthermore, the marauder’s massive, frenetic societies are at the opposite extreme from those of the slow, stealthy Myrmoteras and Acanthognathus. The tempo of an ant species tends to relate to its colony size.12 Workers in small societies tend to be slow and cautious—a sensible way to approach elusive prey like the springtail on a low-energy budget. (Is the per capita energy quota of a small colony indeed likely to be smaller than that of a large one? Picturing a colony as a superorganism, a physiologist might predict that
