Eciton drepanophorum

Smith, F., 1858, Catalogue of the hymenopterous insects in the collection of the British Museum. Part VI. Formicidae., London: British Museum : 149-150

2. Eciton drepanophorum . B.M.

Worker major. Length 4- 4 1/2 lines.-Reddish-yellow, with the head pale testaceous yellow, smooth and shining; very closely resembling E. hamata , but with the scape of the antennae ferruginous: in hamata the antennae are entirely black; the head more narrowed behind, the eyes black, and differing also in having the second node of the abdomen narrower; the mandibles in both species elongate, curved and sickle-shaped.

Worker minor. Length 4- 4 1/2 lines.-Distinguished from the worker of hamata by having the scape ferruginous, the mandibles distinctly denticulated on their inner margin; the second node of the petiole more narrow and elongate.

Hab. Brazil (Ega).

The distinction of this species from hamata rests entirely on a comparison of specimens. Mr. Bates has furnished the following particulars:-" This Eciton is the common species at Ega, its columns of foragers being seen very often, but not daily, in different parts of the forest; it is very nearly allied to a species ticketed 42 ( hamata ), but it differs in always having the basal joint of the antennae pale: in 42 it is always concolorous. The large-headed individuals are always extremely similar one to another, none occurring intermediate in size between them and the small ones. I am quite convinced these large-headed ones are a distinct order of individuals in a colony of Ecitons, and fulfil some distinct, peculiar functions; what those functions are I cannot decide at present; I once saw something of their relations to the rest of the colony in a very large and extraordinary procession. On a clayey piece of ground near the beach, just outside the margins of the forest where the place formed a snug little haven surrounded by high rocks and shrubbery, a dense column of Ecitons descended from amongst the rocks on one side of the harbour, traversing the beach and climbing again the opposite side; the length of the column visible was from 60 to 70 yards, and yet there was no appearance of either the van or the rear of the army; they were all moving in the same direction except a few individuals outside the column, these occasionally ran rearward a short distance, and then again advanced in the direction of the main body: these means were apparently for the purpose of keeping up a current of intelligence along the line. In fact when I disturbed the column, or abstracted an individual, intelligence of the disturbance was very rapidly communicated several yards backwards, and the column at that point commenced retreating. The procession was not a predatory affair, because all the small-headed individuals conveyed in their mandibles a little cluster of white maggots, probably larvae of their own species. I have no doubt of its being a migration, as at the time of observation a change of season was taking place, the river retreating from the beach, and the open places above, about to be burnt up by the hot sun of the dry season.

" The large-headed individuals were in proportion of perhaps about five in one hundred to the small individuals, but not one of them carried anything in its mandibles; they were all trotting along outside the column, and distributed in regular proportion throughout the whole line of army, their globular white heads rendering them very conspicuous among the rest, bobbing up and down as they traversed the inequalities of the road.

" The progress of these ants is not in one simple line when on a foraging expedition, but a line with many branches; a column is occasionally pushed out in the direction of some promising locality. I once observed one of these terminating at a decayed fallen tree; the ants were busy about it, a few having seized some large Formicidae, and also some soft-bodied wasps, these they tore in pieces, and divided the load; the whole column then retired, and re-entered the main line. A branch column is not a party separated from the rest -there is no break in the lines of these ants -but there is always a number passing and repassing, keeping up the line of communication.

" I lately discovered what I imagined was a formicarium of an Eciton : I traced a procession in which many were carrying ova, larvae, and pupae; at a short distance I found the column terminating abruptly, not as I expected at a vast earthy dome, but at a heap of dead leaves in a hard trodden pathway; on the leaves were mustered an unusual number of the large-headed individuals, who resisted my disturbing the leaves with great ferocity. I found under the leaves a large collection of ova, pupae, and larvae, all apparently of one species, certainly a Myrmicide, as the pupae were not enclosed in cocoons; the small-headed workers rapidly gathered up the whole, and a great number of others soon came up, including many of the large-headed fellows, and attacked me most furiously; it was no doubt a temporary store made during a predatory expedition."