the result of chance experience. In some cases two different genera are found in the same nest, with separate chambers and passages, as in the case of the robber-ant (_Solenopsis_) and the slave-ant (_Formica fusca_). The orifices by which the former enter are too small to allow of the entrance of the latter, “hence the robber obtains an easy living at the expense of the larger species,” for “they make incursions into the nurseries, and carry off the larvæ as food.” In a few cases the foundation of a new colony has been carefully watched. Blockmann was successful in observing the formation of new nests by _Componotus ligniperdus_ at Heidelberg. “He found under stones, in the spring, many examples of females, either solitary or accompanied only by a few eggs, larvæ, or pupæ. Further, he was successful in getting isolated females to commence nesting in confinement, and observed that the ant that afterwards becomes the queen, at first carries out by herself all the duties of the nest. Beginning by making a small burrow, she lays some eggs, and when these hatch, feeds and tends the larvæ and pupæ: the first specimens of these latter that become perfect insects are workers of all sizes, and at once undertake the duties of tending the young and feeding the mother, who, being thus freed from the duties of nursing and of providing food while she is herself tended and fed, becomes a true queen-ant. Thus it seems established that, in the case of this species, the division of labour found in the complex community does not at first exist, but is correlative with increasing numbers of the society. Further observations as to the growth of one of these nascent communities, and the times and conditions under which the various forms of individuals composing a complete society first appear, would be of considerable interest.”[93]