ii.] EYE-SPOTS OF CATERPILLARS. 59 



present, are not ripe, and consequently are not touched 

 by birds. Again, in Chcerocampa tersa, there is an eye- 

 spot on each segment, which mimics the flower of the 

 plant on which it feeds (Spermacoce hyssopifolia). White 

 spots, in some cases, 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 daDgerous as food, still, in the number of small green 

 caterpillars which birds love, it would be continually 

 swallowed by mistake. If, on the other hand, it had a 

 conspicuous and peculiar .colour, its evil taste would serve 

 to protect it, because the birds would soon recognize 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 

 euphorbia, with its bitter milky juice, is very distasteful 

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

 striking colours. 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 

 Weismann 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- 



