58 ON PLANTS AND INSECTS. [LECT. 



also resemble the spots of light which penetrate foliage. 

 In other instances, however, and, at any rate, in our 

 elephant hawk-moth, the eye-spots certainly render 

 the insect more conspicuous. Now in some cases, as 

 Wallace has pointed out, this is an advantage, rather 

 than a drawback. Suppose that from the nature of its 

 food or any other cause, as, for instance, from being 

 covered with hair, a small green caterpillar were very 

 bitter, or in any way disagreeable or dangerous as food, 

 still, in the number of small green caterpillars which 

 birds love, it would be continually swallowed by mis- 

 take. If, on the other hand, it had a conspicuous and 

 peculiar color, its evil taste would serve to protect it, 

 because the birds would soon recognise and avoid it, 

 as Weir and others have proved experimentally. I 

 have already alluded to a case of this among the hawk- 

 moths in Deilephila euphorbia, which, feeding on eu- 

 phorbia, with its bitter milky juice, is very distasteful 

 to birds, and is thus actually protected by its bold and 

 striking colors. The spots on our elephant hawk-moth 

 caterpillar do not admit of this explanation, because the 

 insect is quite good to eat I mean for birds. We must, 

 therefore, if possible account for these spots in some 

 other way. There can, I think, be little doubt that 

 Weissmann is right when he suggests that the eye- 

 spots actually protect the caterpillar, by frightening 

 its foes. 



Every one must have observed that these large cater- 

 pillars, as for instance that of Ch.porcellus (Fig. 44), have 

 a sort of uncanny, poisonous appearance ; that they 

 suggest a small thick snake or other evil beast, and the 

 so-called " eyes " do much to increase the deception. 



