It is difficult to estimate the amount of seed stored in a single nest by a colony of ants both on account of the extent of these nests, and because of the number of seeds which are always lost in digging. The nests themselves also vary greatly in size. Perhaps I shall not be very far from the mark however, if I conjecture that average-sized nests contain during the winter months about half a pint of seeds.
Atta structor is more frequently found near houses and in gardens than A. barbara, the latter usually living on wild ground adjoining cultivation. There was a flourishing colony of structor in the main street of Mentone, cleverly placed at the lintel of the door of a corn chandler's store, where they were ever on the look out for stray grains of oats and wheat, which might chance to fall from the sacks. Another nest, in a different part of the town, got its principal subsistence from the grains of canary seed, which were scattered by the birds occupying a cage hanging outside a shop window at a little distance.
Vertical section of an ant's nest. The horizontal lines represent inches of depth.
The granaries of A. structor are arranged in the same way as those of A. barbara, and may, in like manner, be found stored with seeds, and lying at depths below the surface, varying from one to twenty inches.
Plate IV.
A diagram is given in the preceding woodcut of a vertical section of a nest of barbara lying in soil sixteen inches deep, the granaries being at 11/2, 2, 4, 6, 9, and 121/2 inches, as determined by actual measurement on the spot.
In some cases, and especially where the soil is shallow, the galleries and granaries are much crowded together, as is shown in [Plate IV.], which represents a small mass of earth, pierced by the roots of plants, taken out of a nest of barbara, lying at two inches below the surface. When first opened all these granaries were filled with seeds.