THE CATERPILLAR AS MIMIC 



said to be agreeable food. Indeed, as to the latter, 

 what evidence there is points slightly the other way 

 we see many birds finding and feeding freely on 

 the small green caterpillars which in colour match 

 their plant food and station ; perhaps the best counter 

 argument to this is that without the colour matching 

 these caterpillars might be fed on still more freely by 

 birds, and so die out as species. 



Still, there is the fact that some caterpillars, 

 boldly exposing themselves in full daylight, are in 

 gaudy contrast with their surroundings ; and what 

 can the colour and intricate patterns be for, if not 

 for this protection ? The sex problem in caterpillar 

 life does not exist there can be no motive of vanity 

 or rivalry in showing off these gauds. Again, there 

 is, I think, the unquestionable fact that a striking 

 likeness often does exist between a caterpillar and 

 its station. You may see now a caterpillar that sits 

 and feeds on the elm, which matches its environ- 

 ment ; its grey green is that of the underside of the 

 elm leaf ; it is ribbed very like the upper side of the 

 same leaf ; and its station is now on the under, now 

 the upper side of this leaf. Even stretched along 

 the elm tree twig, it seems to harmonize with its 

 surroundings. If the eyes chance to alight on the 

 leaf or twig where this caterpillar sits, it is at once 

 detected ; the mimicry if mimicry it be is not 

 good enough to cheat the prying eye of a human 

 being, much less that of the eager, practised bird ; 

 but if the search is not close and severe, the cater- 

 pillar may well escape detection. 



243 



