As far as the eye can distinguish their tiny forms, troops upon troops of leaves are moving up towards the central point and disappearing down the numerous tunnelled passages. The outgoing empty-handed hosts are partly concealed amongst the bulky burdens of the incomers, and can only be distinguished by looking closely amongst them.”[60] It used to be supposed that these leaves themselves, in a decaying state, were the food of the ants, whilst another theory was that they were used to make a sort of underground roof to the nest with. Belt’s discovery took everybody—including himself—completely by surprise. “I believe,” he says, “the real use they make of them is as a manure, on which grows a minute species of fungus, on which they feed: that they are in reality mushroom growers and eaters”;[60] and he thus narrates the circumstances which led him to this conclusion:— “When I first began my warfare against the ants that attacked my garden, I dug down deeply into some of their nests. In our mining operations we also, on two occasions, carried our excavations from below up through very large formicariums, so that all their underground workings were exposed to observation. I found their nests below to consist of numerous rounded chambers, about as large as a man’s head, connected together by tunnelled passages leading from one chamber to another. Notwithstanding that many columns of the ants were continually carrying in the cut leaves, I could never find any quantity of these in the burrows, and it was evident that they were used up in some way immediately they were brought in. The chambers were always about three-parts filled with a speckled brown flocculent, spongy-looking mass of a light and loosely connected substance. This mass, which I have called the ant-food, proved on examination to be composed of minutely subdivided pieces of leaves, withered to a brown colour and overgrown and lightly connected together by a minute white fungus that ramified in every direction throughout it.”[60] Belt assured himself in many ways, but not through actually seeing them do so, that this fungus was what the ants fed on, and he adds, “that they do not eat the leaves themselves I convinced myself; for I found near the tenanted chambers deserted ones filled with the refuse particles of leaves that had been exhausted as manure for the fungus, and were now left, and served as food for larvæ of _Staphylinidæ_ and other beetles.”[60]