Why it is, in the Insecta, that _islands_[39] should predispose to an apterous state more than continents, it is not easy to speculate. Mr. Darwin has indeed suggested, and with much apparent reason, that, were wings fully developed, the indiscriminate use of them might lead to unhappy results, by tempting the creatures to venture too far from their native rocks; and that, therefore, this partial decay is, under such circumstances, a wise provision in their favour: whilst it has been urged, on the other hand, that since insular species are at all times liable during heavy gales to be blown out to sea, they should in reality be gifted with _stronger_ powers of flight (rather than weaker ones), to fortify them against such disasters; and that, consequently, the above phaenomena are not explicable on Mr. Darwin's hypothesis. For my own part, I am inclined to accept that theory, in all its fullness; and, furthermore, I do not believe that the latter consideration (though it unquestionably contains much presumptive truth) does at all interfere with the admission of it,--seeing that either requirement may be fulfilled, according to the nature of the several species which are destined to be acted upon. Thus, if _flight_ is absolutely indispensable, as in the greater number of the Lepidoptera, and beetles of a flower-infesting tendency, we shall find that the wings remain unaltered (if indeed they be not actually increased in capacity, of which I am by no means certain), and that the effect of isolation is more particularly evident in a diminution of stature. But if, on the contrary, the creatures are less dependent on aerial progression for their sustenance, as in the predacious tribes generally, especially those of nocturnal habits, the reduced area in which they are confined, in conjunction, it may be, with the danger to which they would constantly expose themselves by the promiscuous employment of organs which their modes of life do not positively need, would seem to render the presence of wings unnecessary; and they are accordingly, by degrees, removed:--in which case, however, a compensation for the loss is not unfrequently granted by an increase (more or less perceptible) in bulk.