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The head and jaws, however, are always of the same shape, and a gradation in size is presented from the largest to the smallest, so that all are able to take part in the common labours of the colony.The chief employment of the species seems to be plundering the nests of a large and defenseless ant of another genus (Formica), whose mangled bodies I have often seen in their possession as they were marching away.The armies of Eciton rapax are never very numerous.

Eciton legionis.--Another species, E.legionis, agrees with E.

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but it is much smaller in size, not differing greatly, in this respect, from our common English red ant (Myrmica rubra), which it also resembles in colour.The Eciton legionis lives in open places, and was seen only on the sandy campos of Santarem.The movement of its hosts were, therefore, much more easy to observe than those of all other kinds, which inhabit solely the densest thickets; its sting and bite, also, were less formidable than those of other species.The armies of E.legionis consist of many thousands of individuals, and move in rather broad columns.They are just as quick to break line, on being disturbed, and attack hurriedly and furiously any intruding object, as the other Ecitons.The species is not a common one, and I seldom had good opportunities to watch its habits.The first time I saw an army was one evening near sunset.The column consisted of two trains of ants, moving in opposite directions; one train empty-handed, the other laden with the mangled remains of insects, chiefly larvae and pupae of other ants.I had no difficulty in tracing the line to the spot from which they were conveying their booty:

this was a low thicket; the Ecitons were moving rapidly about a heap of dead leaves; but as the short tropical twilight was deepening rapidly, and I had no wish to be benighted on the lonely campos, I deferred further examination until the next day.

On the following morning, no trace of ants could be found near the place where I had seen them the preceding day, nor were there signs of insects of any description in the thicket, but at the distance of eighty or one hundred yards, I came upon the same army, engaged, evidently, on a razzia of a similar kind to that of the previous evening, but requiring other resources of their instinct, owing to the nature of the wound.They were eagerly occupied on the face of an inclined bank of light earth, in excavating mines, whence, from a depth of eight or ten inches, they were extracting the bodies of a bulky species of ant, of the genus Formica.It was curious to see them crowding around the orifices of the mines, some assisting their comrades to lift out the bodies of the Formicae, and others tearing them in pieces, on account of their weight being too great for a single Eciton-- a number of carriers seizing each a fragment, and carrying it off down the slope.On digging into the earth with a small trowel near the entrances of the mines, I found the nests of the Formicae, with grubs and cocoons, which the Ecitons were thus invading, at a depth of about eight inches from the surface.The eager freebooters rushed in as fast as I excavated, and seized the ants in my fingers as I picked them out, so that I had some difficulty in rescuing a few intact for specimens.In digging the numerous mines to get at their prey, the little Ecitons seemed to be divided into parties, one set excavating, and another set carrying away the grains of earth.When the shafts became rather deep, the mining parties had to climb up the sides each time they wished to cast out a pellet of earth; but their work was lightened for them by comrades, who stationed themselves at the mouth of the shaft, and relieved them of their burthens, carrying the particles, with an appearance of foresight which quite staggered me, a sufficient distance from the edge of the hole to prevent them from rolling in again.All the work seemed thus to be performed by intelligent cooperation among the host of eager little creatures, but still there was not a rigid division of labour, for some of them, whose proceedings I watched, acted at one time as carriers of pellets, and at another as miners, and all shortly afterwards assumed the office of conveyors of the spoil.

In about two hours, all the nests of Formicae were rifled, though not completely, of their contents, and I turned towards the army of Ecitons, which were carrying away the mutilated remains.For some distance there were many separate lines of them moving along the slope of the bank-- but a short distance off, these all converged, and then formed one close and broad column, which continued for some sixty or seventy yards, and terminated at one of those large termitariums or hillocks of white ants which are constructed of cemented material as hard as stone.The broad and compact column of ants moved up the steep sides of the hillock in a continued stream; many, which had hitherto trotted along empty-handed, now turned to assist their comrades with their heavy loads, and the whole descended into a spacious gallery or mine, opening on the top of the termitarium.I did not try to reach the nest, which I supposed to lie at the bottom of the broad mine, and therefore, in the middle of the base of the stony hillock.

Eciton drepanophora.--The commonest species of foraging ants are the Eciton hamata and E.drepanophora, two kinds which resemble each other so closely that it requires attentive examination to distinguish them; yet their armies never intermingle, although moving in the same woods and often crossing each other's tracks.

The two classes of workers look, at first sight, quite distinct, on account of the wonderful amount of difference between the largest individuals of the one, and the smallest of the other.