Sometimes a still more wonderful arch or tunnel is made by the ants, for it is a living one composed of the bodies of some of their number. These, apparently, stand in two rows upon their hinder legs, and by interlocking their jaws and intertwining their anterior legs and antennæ make a covered way for the workers to pass along. From this, it would appear that certain of the ants feel the heat less than the ordinary workers. Apparently, however, the ants only act in this way when the sky is clouded, and when, as a consequence, one would not have expected any covering to be necessary. Dr. Savage, who gives this interesting account of ant body-building, as one may call it, has not been sufficiently explicit in regard to the details and circumstances attending it. More extraordinary even than their habit of making a living arch or gallery, is the method which these ants employ of passing rivers. To do this they climb a tree upon one or other of its banks, and running out along a branch overhanging the water, let themselves down by clinging one to another, until a rope is formed of their united bodies. This soon reaches the water, and becoming constantly longer as fresh ants run down and affix themselves, is swept out from the shore by the force of the current, until at length its free end is washed against the opposite bank. There is, now, a thin bridge of ants, like a ribbon and of immense length, stretched slanting-wise from shore to shore, and over it the main body of the ants ceaselessly pass, till there are no more to come. Only the bridge itself now remains, but the ants helping to form this, on the nearer side of the stream, detach themselves now from the tree, when the bridge changes to a rope in the water, and this, being carried at once down the stream, is soon washed against the further bank, to which its corresponding end is attached.[6] As soon as this has been accomplished, the living ants composing this organic work of engineering skill, crawl on shore and continue their march, bringing up the rear of the column. It has been asserted, I know—for I have read it somewhere, and well remember the accompanying illustration—that the monkeys inhabiting the Brazilian forests are accustomed to cross the smaller rivers that flow through them, in the same way. As the ants do so, there seems nothing absolutely impossible in the thing, but as years have gone by and I have met with no reference to so interesting a fact in any work of standing, I have got to distrust the only authority I can remember for it—a boy’s book, namely, by Mayne Reid.