It is evident, from the foregoing outline, that the insects of South Temperate America, more than any other class of animals, exhibit a connection with the north temperate regions, yet this connection is only seen in certain groups. In Diurnal Lepidoptera and in Carabidæ, the northern element is fully equal to the tropical, or even preponderates over it. We have already suggested an explanation of this fact in the case of the Carabidæ, and with the butterflies it is not more difficult. The great mass of Neotropical butterflies are forest species, and have been developed for countless ages in a forest-clad tropical country. The north temperate butterflies, on the other hand, are very largely open-country species, frequenting pastures, mountains, and open plains, and often wandering over an extensive area. These would find, on the higher slopes of mountains, a vegetation and conditions suited to them, and would occupy such stations in less time than would be required to adapt and modify the forest-haunting groups of the American lowlands. In those groups of insects, however, in which the conditions of life are nearly the same as regards both temperate and tropical species, the superior {48}number and variety of the tropical forms has given them the advantage. Thus we find that among the Lucanidæ, Buprestidæ, and Longicorns, the northern element is hardly perceptible. Most of these are either purely Neotropical, or allied to Neotropical genera, with the admixture, however, of a decided Australian element. As in the case of the Amphibia and fresh-water fishes, the Australian affinity, as shown by insects, is of two kinds, near and remote. We have a few genera common to the two countries; but more commonly the genera are very distinct, and the affinity is shown by the genera of both countries belonging to a group peculiar to them, but which may be of very great age. In the former case, we must impute some of the resemblance of the two faunas to an actual interchange of forms within the epoch of existing genera--a period of vast and unknown duration in the class of insects; while in the latter case, and perhaps also in many of the former, it seems more in accordance with the whole of the phenomena, to look upon most of the instances as survivals, in the two southern temperate areas, of the relics of groups which had once a much wider distribution. That this is the true explanation, is suggested by the numerous cases of discontinuous and scattered distribution we have had to notice, in which every part of the globe, without exception, is implicated; and there is a reason why these survivals should be rather more frequent in Australia and temperate South America, inasmuch as these two areas agree in the absence of a considerable number of otherwise cosmopolitan vertebrate types, and are also in many respects very similar in climatic and other physical conditions. The preponderating influence of the organic over the physical environment, as