My next glance into the pit showed a large toad, squatted on a small shelf of sand, close to the edge of a crowded column of ants. He was a rough old-chap, covered with warts and corrugations, and pigmented in dark gray, with mottlings of chocolate and dull red and occasional glints of gold. He was crouched flat, with all his fingers and toes tucked in beneath him. His head was drawn in, his eyes closed, and all his exposed surface was sticky with his acid perspiration—the sweat of fear. He knew his danger—of that there was no doubt—and he was apparently aware of the fact that he could not escape. Resignedly he had settled on the very line of traffic of the deadly foe, after intrenching himself and summoning to his aid all the defenses with which nature had endowed him. And he was winning out—the first vertebrate I have ever known to withstand the army ants. For a few minutes he would be ignored and his sides would vibrate as he breathed with feverish rapidity. Then two or three ants would run toward him, play upon him with their antennæ, and examine him suspiciously. During this time he was immovable. Even when a soldier sank his mandibles deep into the roughened skin and wrenched viciously, the toad never moved. He might have been a parti-colored pebble embedded in its matrix of sand. Once, when three bit him simultaneously, he winced, and the whitish, acrid juice oozed from his pores. Usually the ants were content with merely examining him. I left him when I saw that he was in no immediate danger.
One other creature was quiescent in the pit and yet lived: a big, brown, hardbacked millipede. Like the frog, he fully realized his danger and had sunk his bulk partly into the sand, bending down head and tail and presenting only mailed segments. A mob of ants were trying vainly to bite their way into this organic citadel.
For the dozens of grasshoppers, crickets, roaches, beetles, spiders, ants, and harvest men, there was no escape. One daddy-long-legs did a pitiful dance of death. Supported on his eight long legs, he stood high out of reach of his assailants. He was balanced so exactly that the instant a feeling antenna touched a leg, he would lift it out of reach. Even when two or three were simultaneously threatened, he raised them, and at one time stood perfectly balanced on four legs, the other four waving in air. But his kismet came with a concerted rush of half a dozen ants, which overbore him, and in a fraction of time his body, with two long legs trailing behind, was straddled by a small worker and borne rapidly away.
I now flattened myself on an antless area at the edge of the pit and studied the field of battle. In another half-hour the massacre was almost over. Five double, and often quadruple, columns were formed up the sandy cliffs, and the terrific labor of carrying out the dead victims began. The pit was five feet deep, with perfectly straight sides, which at the rim had been gutted by the rain, so that they actually overhung. Yet the ants which had half-climbed, half-tumbled and rolled their way to the bottom in the wake of their victims, now set themselves to solving the problem of surmounting these cliffs of loose, crumbling grains, dragging loads which, in most cases, were much heavier than themselves. Imagine a gang of men set to carrying bundles of one to two hundred pounds up perpendicular cliffs twelve hundred feet in height, and the task of the army ants is made more vivid. So swiftly did they work and so constantly shifted their formations and methods of meeting and surmounting difficulties, that I felt as I used when looking at a three-ring circus. I could perceive and record only a small part of the ingenious devices and the mutual assistance and sharing of the complicated conditions which arose at every step.
Among the frightened victims, even for those endowed with excellent eyesight and powerful flight, there was only hopeless confusion and blind terror. Instead of directing their flight upward, they drove from side to side. Those whose leaps should have carried them out, simply kicked out blindly and brought up against the sandy walls.
If leaf-cutting ants had been at work here, there would have been a certain amount of cooperation. Certain ones would have cut leaves, other individuals would have picked them up and transported them. But with the army ants this mutual assistance was sublimated, developed to a quintessence of excellence. If I, seated on the rim, overlooking the whole, had been an all-powerful spirit, gifted with the ability to guide by thought simultaneously all the ants within sight, such guidance could not have bettered the cunning cooperation, the unexpectedly clever anticipation of trouble, the marvelous singleness of purpose and manifold effectiveness exhibited by these astounding creatures.
First, as to the personnel of the army ants. Roughly I divided them into two categories, white-heads and black-heads. The latter were by far the more numerous and, as a rule, were smaller, with less powerful jaws. But this did not mean that the white-heads were all soldiers. Most of them indeed were the hardest workers. Between the great extremes of size in each of these two types, there seemed to exist only a difference of degree. The smallest black-head laborers, only a little more than one-fifth of an inch long, did their bit, flew like bull pups at any prey which showed signs of life, and staggered bravely along with any piece of loot which their short legs could straddle.
The white-heads, twice as large, were the strong men of the community, putting all their activity into the labor, shouldering, pushing, dragging, lifting, singly or in unison. These persons had powerful jaws, but jaws which were stout and scissor-edged. The largest of the white-heads were armed with reaping-hooks, long inwardly-pronged jaws, curved like the tushes of ancient mammoths, too specialized for carrying loads, but well adapted for defense of the most powerful character. Yet, as we shall see, even these were not too proud to work, when occasion demanded it. But their jaws were so enormous that they had to carry themselves very erect, and they could not make quite as good time as the other castes.
All had reddish brown abdomens, with darker thoraxes and white or black heads. These heads bulged on each side like the domes of observatories. Exactly in the center of each dome, looking like the jet-black head of a tiny pin, was the single remaining facet of the eye, the degenerate residue of the hundreds which were present in their ancestors, and which the perfect males and females still possess and look through. Even this single eye is a sham, for its optic nerve dies out before the brain ganglion is reached; so we come to the astounding realization that these ants are totally blind, and carry on all their activities through the sense or senses residing in those marvelous quivering antennæ. Here are beings spending all their lives in ceaseless changing activities, meeting and coping with constantly new conditions, yet wholly blind. Their sense of smell dominates their judgment of substance, and the moment an army ant reached my moccasin he sank jaws and sting deep into the fabric as instinctively and instantly as when he executed the same manœuvers more effectively on my hand.
Keeping this handicap in mind, the achievements of these little creatures assumed a still greater significance, and with renewed interest and appreciation I again surveyed the scene in the amphitheater before me. When the majority of the pit victims had been slain, the process of carrying them up to the surface began. The hordes of ravening ants resolved themselves, as I have said, into five distinct columns of traffic which, inch by inch, fought for a footing up three of the four sides.