In such cases the sympathetic colouring was probably the first to arise, and the eye-spot was developed later by a new process of selection, brought about by the necessity of protecting the species more effectively than by mere inconspicuousness alone. In many cases it can be proved that the power of scaring off an enemy did not begin with the formation of the eye-spot, but with the development of a new instinct. When the caterpillar of _Chærocampa elpenor_ is attacked it immediately assumes the defiant attitude described above, but the same striking attitude is assumed by the caterpillars of the allied American genus _Darapsa_, as I learn from an old illustration by Abbot and Smith, although this form possesses no eye-spots (Fig. 7). Thus, then, metaphorically speaking, the caterpillar at first attempted to scare off its enemy by a terrifying attitude alone, and it was only subsequently, in the course of the phyletic evolution, that the eye-spots were added, in the elephant hawk-moths and other species, to heighten the terrifying effect. But that the eye-spot did not make its appearance suddenly is proved by several American species of _Smerinthus_, in which they are much less perfectly developed than in the European species. In these Sphingidæ, too, the defiant attitude was evolved earlier than the eye-spots, as we may see from our poplar hawk-moth (_Smerinthus populi_), which, when alarmed, spreads out all four wings in the same peculiar manner which in the eyed hawk-moth (_Smerinthus ocellatus_) displays the eye-spots; it strikes about with its wings as if to scare off the enemy, an effect which will certainly be more surely achieved if, at the same time, a pair of eyes becomes suddenly visible.