34 2 Studies in the Theory of Descent. 



perhaps give support to this view. As these 

 insects are not protectively coloured, this habit 

 would long ago have led to their extermination ; 

 instead of this, however, we find that in all 

 situations favourable to their conditions of life 

 they are among the commonest of the Sphingidcz. 



Thus, D. Euphorbia occurs in large numbers 

 both in South and North Germany (Berlin) ; and 

 Dr. Staudinger informs me that in Sardinia the 

 larvae of D. Dahlii were brought to him by 

 baskets full, 



But if the conspicuous ring-spots (combined of 

 course with the other bright colours) may be 

 regarded as signals of distastefulness in many 

 species of Deilephila, this by no means excludes 

 the possibility that in some species these markings 

 play another part, and are effective as a means 

 of alarm. It even appears conceivable to me 

 that in one and the same caterpillar they may 

 play both parts against different foes, and it 

 would certainly be of interest to confirm or refute 

 this supposition by experiment. 



In the light yellow variety of the caterpillar 

 of D. Galii the ring-spots may serve as means of 

 alarm, and still more so in that of D . Niccza, the 

 resemblance of which to a snake has struck earlier 

 observers. 14 



14 Thus, Boisduval states of this caterpillar, which in Provence 

 lives on Euphorbia esula and allied species : " Its resem- 

 blance to a serpent, and its brilliant colour, permit of its being 



