70 



THE EVOLUTION THEORY 



by the sympathetically coloured parts— in this instance the anterior 

 wings. In other cases eye-spots of considerable size lie clearly 

 exposed, but exhibit the same sympathetic colours as the whole of the 

 rest of the wing-surface. In this case they do not interfere with the 

 protective influence of general colouring, because they are only visible 

 from a very short distance. This is the case in the large Caligo 

 species of South America, which only fly for a short time in the early 

 morning and in the evening, remaining concealed throughout the day 

 in dark shadowy places, where the mingled colouring of brown, grey, 

 yellow, and black on the under surfaces of the wings prevents their 

 being recognized from a distance as butterflies at all. But even the 



best sympathetic colouring is not 

 an absolute protection, and when 

 the insect is discovered by an 

 enemy near at hand, the terrify- 

 ing mark, a large deep-black spot 

 on the posterior wing, comes into 

 effect, and scares the assailant 

 away. 



In such eases 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 efiectively than by mere in- 

 conspicuousness 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 de- 

 velopment of a new instinct. When the caterpillar of Chcerocampa 

 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 cater- 

 pillar at first attempted to scare off its enemy by a terrifying attitude 

 alone, and it was only subsequently, in the course of the phyletic evo- 

 lution, that the eye- spots were added, in the elephant hawk-moths 

 and other species, to heighten the terrifying efiect. But that 

 the eye-spot did not make its appearance suddenly is proved by several 



Fig. 6. 



Caligo. 



Under surface of the wings of 



