On the other hand, Mr. Tennant tells us that Formica smaragdina, in forming its dwellings by cementing together the leaves of growing trees, adopts the following method: A line of ants, standing along the edge of one leaf, seize hold of another, and bring its margin in contact with the one on which they are posted. They then hold both together with their mandibles, while their companions glue them fast with a kind of adhesive paper which they prepare. If the two leaves are so far apart that a single ant cannot reach from one to another, they form chains with their bodies to span over the gap. The same author also informs us that certain Ceylonese ants, when carrying sand or dry earth for the construction of their nests, glue several grains together so as to form a lump as large as they can carry, and thus economize time and labor.
Mr. Belt, in his "Naturalist in Nicaragua" (page 27), gives the following account of the manner in which the Ecitons, or foraging 'ants of Central and South America, deal with what may be called engineering difficulties: "I once saw a wide column trying to pass along a crumbling, nearly perpendicular slope. They would have got very slowly over it, and many of them would have fallen, but a number having secured their hold and reaching to each other remained stationary, and over them the main column passed. Another time they were crossing a water-course along a small branch, not thicker than a goose-quill. They widened this natural bridge to three times its width, by a number of ants clinging to it and to each other on each side, over which the column passed three or four deep; whereas, except for this expedient, they would have had to pass over in single file, and treble the time would have been consumed."
Again, in Eciton legionis, according to Mr. Bates, when digging mines to get at another species of ant whose nests they were attacking, the workers were 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 burdens, 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."
What, then, are we to learn from these somewhat inconsistent cases? Are we to conclude that Sir John Lubbock, Mr. Belt, Mr. Bates, and Mr. Tennant, must be careless and incompetent observers? Assuredly not. Are we to believe that ants are stupid, irrational creatures, and that when they do anything right it must be regarded as an accident or ascribed to that convenient phantom, instinct? Still less: the well-established cases which are on record agree badly with either of these suppositions. The true explanation of the diffi-
