Oecodoma cephalotes

1. Oecodoma cephalotes. Pl. X. figs. 21-23. B.M.

Formica cephalotes, Lin. Syst. Nat. i. 964. 15 [[worker]], major.

Fabr. Syst. Ent. 395. 22; Spec. Ins. i. 493. 31; Mant. i. 310. 38; Ent. Syst. ii. 362. 52.

De Geer, Mem. Ins. iii. 604. 5. t. 31. f. 11 [[worker]].

Oliv. Encycl. Meth. vi. 499. 47.

Latr. Hist. Nat. Fourm. 222. pt. 9. f. 57. A. Formica fervens, Drury, Illust. Exot. Ins. iii. t. 42. f. 4 [[queen]]. Formica migratoria, Le Geer, Ins. iii. 604. 5. t. 31. f. 11 [[worker]]. Formica grossa, Oliv. Encycl. Meth. vi. 499. 35 [[queen]]; Fabr. Ent.

Syst. ii. 359. 40. Atta cephalotes, Fabr. Syst. Piez. 421. 1 [[worker]].

Latr. Gen. Crust, et Ins. iv. 124.

Guer. Icon. Reg. Anim. iii. 422. 1.

Erichs. Faun, et Flo. Brit. Guiana, iii. 593. Madame Merian, tab. 18; Seba, iv. t. 99. f. 6.

Hab. Brazil; Mexico.

" Oecodoma cephalotes is the common species of the genus; it is abundant in light soils, and especially cultivated grounds. Its formicaria are very extensive and wholly subterraneous, the site being marked on the surface of the ground only by a mound of little elevation formed of earth, generally lighter in colour than the surrounding soil, raised in little ridges and turrets. The space occupied by the mound is always cleared of foliage; the entrances appear to be at a distance from the mounds, and con- sequently there must be a system of subterranean highways. The Oecodomae appear to be exclusively herbivorous, and, like the Cryptoceri, have no stings; what they do with the immense amount of cut leaves they are perpetually conveying to their abode it is impossible to divine. Probably they prepare food for the larvae from the leaves; but besides leaves and fruits, in- dividuals in the processions may be frequently seen conveying dried twigs and leaves, and in rare instances, dried fragments of insects; what they especially delight in is the dried grain of the Mandiocca meal, the general food of the inhabitants of this country. This insect, from its ubiquity, immense numbers, eternal industry, and its plundering propensities, becomes one of the most important animals in Brazil; its immense hosts are unceasingly occupied in defoliating trees, and those most relished by them are precisely the useful and cultivated kinds; they have regular divisions of labourers: numbers mount the trees and cut off the leaves in irregularly rounded pieces about the size of a shilling, another relay of labourers carry them off as they fall; sometimes these latter get behindhand with their work, and the fallen pieces accumulate to a great heap; such heaps used to puzzle me when I met with them on first arriving in this country. I had thought Oecodoma exclusively herbivorous, but I ou one occasion surprised one dragging off the dead body of a fine Lamia nearly an inch long."

The following remarks apply to the workers of the species which appears to be the Oecodoma cephalotes of authors; they certainly apply to that species of this catalogue: -

" I send you all the different sizes of this species taken from the formicarium. The medium-sized individuals were occupied in cutting pieces of leaf of the size of a sixpence. The minute individuals were few in number at the leaf-cutting operations, but were in vast numbers about the entrance to the dome of the formicarium: the very large-headed ones were not engaged in leaf-cutting, nor were they to be seen in the processions; they were only to be seen on disturbing the nest.

" I had observed during several months the workers of this species, at a place in the forest, occupied in cutting pieces of the foliage of trees, and always crossing the pathway in the same direction along a fallen tree. I at length determined to trace the procession through the jungle to their formicarium; this I soon discovered; it was very different in appearance and much inferior in size to the vast mounds thrown up by the species found at Para and Santarem (E. cephalotes?). The dome of the nest of this species is only about a foot in diameter, and about the same in height; it is formed of light earth, matted and thatched as it were with pieces of leaves which the workers cut and carry. I watched the heavily-laden fellows as they came trooping in, and found they all deposited their load in a heap close to the mound. I then searched for the entrance to the interior; I found, after removing a little of the surface, three burrows, each about an inch in diameter; half a foot downwards all three united in one tubular burrow, about four inches in diameter; to the bottom of this I could not reach when I probed with a stick to the depth of four or five feet. The tube of the main burrow was perfectly smooth, and covered with a vast number of workers of much smaller size than those occupied in conveying the leaves: these minute individuals were unmixed with any of the larger size. Afterwards, on probing lower into the burrow, up came, one by one, several gigantic fellows, out of all proportion larger than the largest of those at work outside, and which I could not have supposed to belong to the same species. Besides the greatly enlarged size of the head, the sculpture of the body is very dif- ferent, and what struck me as very curious, they have an ocellus in the middle of the forehead; this latter feature, added to their startling appearance from the cavernous depths of the formi- carium, gave them quite a Cyclopean character. There are, however, individuals intermediate in size between these and the other workers."

An examination of the workers collected by Mr. Bates shows, that although the smaller workers differ in size, from two-tenths of an inch to five-tenths, yet none of these have an ocellus in the forehead, and the larger individuals having an ocellus scarcely differ among themselves in size.

The large worker of this species may be known from that of Oe. sexdentata, by having an ocellus, a more polished head, and by having the mandibles of the same colour as the head, with the teeth black; Oe. sexdentata has the anterior margin of the face and the mandibles blackish-brown or black; the colour of the mandibles alone will serve to separate the small workers.