able to secure better specimens of the tunnels for drawing (Figs. B, B 1, Plate V., p. 33). These drawings may be taken as representing also the size and shape of the tunnels in the former nest, which were for the most part like these, beautifully cylindrical, as is shown in the front view of the tunnel at B 1. In one nest of barbara I found a curious hollow spherical dome, about an inch in diameter, the walls of which were constructed of hardened earth about two lines thick, and having a large circular aperture at the top and a very small one below (Figs. D and D 1, Plate VI.). This dome was imbedded below in earth which adhered to it, but it was otherwise easily separable from the soil; its inner walls were smoothed with great nicety.
It has been suggested to me that this spherical chamber was originally the work of a scarabæus, which had chanced to bury the ball containing its eggs close to the nest of the ants, and that the latter had appropriated it after the departure of the beetle grubs. This may perhaps have been the case, but the dome was rather larger than the ball usually formed by the scarab beetle, and I have never seen one of these balls surrounded by a hardened case. The chamber thus constructed was employed as a granary, and filled, as well as the adjacent passages, with the grain of a grass (Tragus racemosus), still enclosed in the husks, among which I detected several ants at work, and also some minute white semi-transparent creatures, like spring-tails (Podurus), which abound in these ants' nests. Besides this spring-tail it is common to find in the galleries and granaries of Atta structor and A. barbara, certain silky yellowish-white "silver fish" (Lepisma), a small white woodlouse which does not
