At one time I suspected that the elater larvæ might consume the seeds stored by the ants, and I therefore confined some of them in a tumblerful of earth and seeds; but at the end of three weeks, though the larvæ were strong and healthy-looking, I could not detect that any of the seeds had been touched, and even those which had sprouted remained uninjured. I have searched in vain for the beetles and staphylinidæ which are known to inhabit certain ant's nests. In one nest I found (on Dec. 28) a quantity of small spherical, egg-like galls, slightly larger than but resembling the fruit of _Fumaria capreolata_, spotted with pink-brown on a yellowish or greyish ground. There was a dark spot at the point at which the mature insect would emerge, and one did escape from the egg-like cocoon while I was watching, and proved to be a _Cynips_ of very small size, but furnished with a terrible dart for puncturing its prey. It seems difficult to understand how it comes that these galls are systematically placed among the seeds, for it was evidently no chance occurrence, and I can only conjecture that the worker ants may have brought them in and stored them under the impression that they were really seeds! Even ants make mistakes, and of this I have given an example above (p. 19). Though I have frequently found colonies of several distinct species of ants inhabiting nests made in the earth traversed by the widespread galleries of _Atta structor_ and _barbara_, I have never detected any intermixture of species in the chambers of a nest,[31] and but rarely found even the galleries and entrance used in common by more than one species. On one occasion when opening a nest of _structor_ I cut through a colony of the tiny, large-headed, yellow ant _Pheidole megacephala_, lying in the midst of, though distinct from, the former. When, however, it chanced that one of the _structors_ fell from the crumbling earth into the midst of the _Pheidoles_, it was curious to see how fiercely it would be attacked, and with what terrified speed it would scamper off, without attempting any resistance, and often carrying two or three _Pheidoles_ hanging on to its legs. [Footnote 31: Except in a few cases where I have seen one or two _structors_ in nests of _barbara_ and _vice versâ_, and in the curious instance to be mentioned below, where one colony consisted of nearly equal parts of _structor_, _barbara_, and the red-headed variety of _barbara_.] Accidentally in this way battles do sometimes take place between ants of different species; but by far the most savage and prolonged contests which I have witnessed were those in which the combatants belong to two different colonies of the same species.