There are dwarfs not more than one-fifth of an inch in length, with small heads and jaws, and giants half an inch in length with monstrously enlarged head and jaws, all belonging to the same brood.There is not, however, a distinct separation of classes, individuals existing which connect together the two extremes.
These Ecitons are seen in the pathways of the forest at all places on the banks of the Amazons, travelling in dense columns of countless thousands.One or other of them is sure to be met with in a woodland ramble, and it is to them, probably, that the stories we read in books on South America apply, of ants clearing houses of vermin, although I heard of no instance of their entering houses, their ravages being confined to the thickest parts of the forest.
When the pedestrian falls in with a train of these ants, the first signal given him is a twittering and restless movement of small flocks of plain-coloured birds (ant-thrushes) in the jungle.If this be disregarded until he advances a few steps farther, he is sure to fall into trouble, and find himself suddenly attacked by numbers of the ferocious little creatures.
They swarm up his legs with incredible rapidity, each one driving his pincer-like jaws into his skin, and with the purchase thus obtained, doubling in its tail, and stinging with all its might.
There is no course left but to run for it; if he is accompanied by natives they will be sure to give the alarm, crying "Tauoca!"and scampering at full speed to the other end of the column of ants.The tenacious insects who have secured themselves to his legs then have to be plucked off one by one, a task which is generally not accomplished without pulling them in twain, and leaving heads and jaws sticking in the wounds.
The errand of the vast ant-armies is plunder, as in the case of Eciton legionis; but from their moving always amongst dense thickets, their proceedings are not so easy to observe as in that species.Wherever they move, the whole animal world is set in commotion, and every creature tries to get out of their way.But it is especially the various tribes of wingless insects that have cause for fear, such as heavy-bodied spiders, ants of other species, maggots, caterpillars, larvae of cockroaches and so forth, all of which live under fallen leaves, or in decaying wood.The Ecitons do not mount very high on trees, and therefore the nestlings of birds are not much incommoded by them.The mode of operation of these armies, which I ascertained only after long-continued observation, is as follows: the main column, from four to six deep, moves forward in a given direction, clearing the ground of all animal matter dead or alive, and throwing off here and there a thinner column to forage for a short time on the flanks of the main army, and re-enter it again after their task is accomplished.If some very rich place be encountered anywhere near the line of march, for example, a mass of rotten wood abounding in insect larvae, a delay takes place, and a very strong force of ants is concentrated upon it.The excited creatures search every cranny and tear in pieces all the large grubs they drag to light.It is curious to see them attack wasps'
nests, which are sometimes built on low shrubs.They gnaw away the papery covering to get at the larvae, pupae, and newly-hatched wasps, and cut everything to tatters, regardless of the infuriated owners which are flying about them.In bearing off their spoil in fragments, the pieces are apportioned to the carriers with some degree of regard to fairness of load: the dwarfs taking the smallest pieces, and the strongest fellows with small heads the heaviest portions.Sometimes two ants join together in carrying one piece, but the worker-majors, with their unwieldy and distorted jaws, are incapacitated from taking any part in the labour.The armies never march far on a beaten path, but seem to prefer the entangled thickets where it is seldom possible to follow them.I have traced an army sometimes for half a mile or more, but was never able to find one that had finished its day's course and returned to its hive.Indeed, I never met with a hive; whenever the Ecitons were seen, they were always on the march.
I thought one day, at Villa Nova, that I had come upon a migratory horde of this indefatigable ant.The place was a tract of open ground near the river side, just outside the edge of the forest, and surrounded by rocks and shrubbery.A dense column of Ecitons was seen extending from the rocks on one side of the little haven, traversing the open space, and ascending the opposite declivity.The length of the procession was from sixty to seventy yards, and yet neither van nor rear was visible.All were moving in one and the same direction, except a few individuals on the outside of the column, which were running rearward, trotting along for a short distance, and then turning again to follow the same course as the main body.But these rearward movements were going on continually from one end to the other of the line, and there was every appearance of there being a means of keeping up a common understanding amongst all the members of the army, for the retrograding ants stopped very often for a moment to touch one or other of their onward-moving comrades with their antennae-- a proceeding which has been noticed in other ants, and supposed to be their mode of conveying intelligence.When I interfered with the column or abstracted an individual from it, news of the disturbance was very quickly communicated to a distance of several yards towards the rear, and the column at that point commenced retreating.All the small-headed workers carried in their jaws a little cluster of white maggots, which I thought at the time, might be young larvae of their own colony, but afterwards found reason to conclude were the grubs of some other species whose nests they had been plundering, the procession being most likely not a migration, but a column on a marauding expedition.
