Among the many curious and obscure features in the economy of ants, one of the most interesting is the occasional presence in their nests of different creatures which live among and often in harmony with them, the nature of the relations between host and guest being for the most part quite unknown. When examining the contents of some granaries from an extensive nest of _Atta structor_ at Mentone last spring (1874), I found large numbers of a minute, shining-brown beetle moving about among the seeds. These little creatures were themselves not unlike some very small seeds, and were of an elliptic form, measuring a trifle less than one line in length. They proved to belong to the scarce and very restricted genus _Coluocera_.[118] This species, named by Kraatz _C. attæ_, on account of its inhabiting the nests of ants belonging to the genus _Atta_, has been found in Greece. [Footnote 118: I am indebted to Mr. F. Smith of the British Museum for the name of this beetle and for the following reference to its description; Kraatz in _Berliner Entomologische Zeitschrift_ for 1858-9, p. 140.] Mr. Bates,[119] in his most interesting account of his travels on the Amazons, remarks upon the singular fact, of which the above instance is an example: "that some of the most anomalous forms of Coleopterous insects are those which live solely in the nests of ants," and he then goes on to allude to the strange snake _Amphisbæna_, a native of that region, which also lives in the nests of the Sauba ants (_Œcodoma cephalotes_), observing how curious it is that an abnormal form of snakes should be found in the society of these insects. He is of opinion, however, that the _Amphisbæna_ is not an inoffensive guest, but lives upon the ants whose nest it selects for its home. [Footnote 119: _Naturalist on the Amazons_, p. 61-2 (Ed. 2, 1864).] Another remarkable inhabitant of ants' nests is a minute cricket, of which I found a single example in the midst of a colony of black ants at Mentone in February, 1874. This miniature cricket is scarcely as large as a grain of wheat, the body, excluding the antennæ and other appendages, measuring only two lines in length. It has been described by Dr. Paolo Savi[120] under the name of _Gryllus myrmecophilus_. He detected it in the nests of several species of ants in Tuscany, where it lived on the best terms with its hosts, playing round their nests in warm, and retiring into them in stormy weather, while allowing the ants to carry it from place to place during their migrations. [Footnote 120: Dr. P. Savi, _Osservazione sopra la Blatta acervorum di Panzer_ in _Bibliotheco Italiana_, tom. xv. p. 217.] _Gryllus myrmecophilus_ has also been observed in nests of the turf ant (_Tetramorium cæspitum_) near Paris.[121] [Footnote 121: _Bulletin Soc. Entom. de France_ (1872), p. li.]