Adventures Among Ants - Mark W. Moffett [107]
Polyergus queens, however, have retained their workers. I assume there must be a downside to keeping a breeding stock of slave queens around. Perhaps Amazon nests that retain a slave queen are subject to insurrection, in which case it wouldn’t pay for the slavemaker to share reproductive control, the ultimate source of power in an ant society.
13 abduction in the afternoon
A week into my stay at California’s Sagehen Creek, I was lounging among the grass tufts next to a Polyergus breviceps ant nest with Faerthen Felix, the station’s assistant manager. I was trying to determine exactly how their raids transpire, and we had shown up early to catch the moment when the action began. But for most of the day not a single Amazon had shown her face. When the first slavemaker appeared at 4 P.M., she showed a supreme indifference to the slaves that were industriously collecting bits of my jelly sandwich. By 4:45, a hundred Amazons were milling about. While the foraging slaves went far afield, the Amazons stayed within 2 to 3 meters of their nest entrance.
That had been the habit of every colony I’d observed: no Amazon ants most of the day, then a slow buildup of milling workers near the nest late in the afternoon. Faerthen and I tried to figure out what all the wandering Amazons were doing. In time, the raid would depart, and they would join it, but until then they occupied their time examining every cranny near the nest. Were they foraging? Faerthen asked. No: finding meals is slaves’ work. The milling ants never picked up a thing, nor was there any indication that they laid trails or took notice of one another. Was their exploration part of colony defense? Perhaps. I had heard that when raiding workers encounter another Amazon colony, they attempt to destroy it and carry off its brood as a source of slaves of their own kind.1 So I dropped an alien Polyergus in front of the milling workers to see if they would respond—and was not surprised, given the threat she represented to their colony, that they immediately punctured her to death.
This Amazon worker is positioning her daggerlike mandibles to pierce the head of an ant from an alien nest. Her own head has already been punctured behind the eye.
But as this was the extent of their safeguarding activities, there had to be a better explanation for the slavemakers’ desultory bustle. I would find that Amazon colonies raid almost simultaneously at the end of each day, with virtually every wanderer joining in. By the time the raiders from one colony have gone far enough to encounter a competing nest, the raiders from that second colony have probably departed along their own path. Protection against other Amazon colonies must depend chiefly on the surfeit of workers that never leave the nest.
If not foraging or supplying defense, what do the milling Amazons accomplish? Watching their incessant scrambling within this staging area, I proposed to Faerthen that they might be energizing themselves for the upcoming battle. That would make them a bit like human troops performing drills—sharing movements and chants, a practice known to deepen identification with the regiment.2 Wolves and wild dogs engage in similar rallies, which assure that everyone is “awake, alert, and ready” before a hunt.3 In any case, after this seeming display of bravado, which typically ended between 5 and 6 P.M., the raid started fast and moved quickly.
The first indication of an incipient raid is a surge of Amazon workers in one direction, with the milling ants in that quadrant joining an outpouring from the nest. The exodus bears some similarity to the way a raid explodes from an army ant bivouac, except that with Amazon ants, in the few minutes after most of the milling ants join the raid, the number of ants lagging behind declines to zero. A stream of workers a few meters long moves away from the nest like a swift snake, albeit one that is straight as