most natural, as naked larvae are far more acceptable to most insect-eating 

 birds, and the very hairy ones are to a large degree protected by their hairs 

 alone, and have much less need of deceptive coloration. (It should be noticed, 

 however, that, whether by coincidence or not, certain hairy larvae bear a strong 

 mimetic resemblance to details of their environment. Thus some of the furry, 

 white or yellowish grass-caterpillars look wonderfully like the fuzzy flower- 

 heads of the grass on which they feed, or of other species of grass sure to be 

 common in the same field.) 



The same great fundamental principle of protective coloration, which is the 

 essential root of the matter in the case of the vertebrate orders we have been 

 considering, namely the principle of oUiterative shading, holds, to a very large 

 extent, among lepidopterous larvae. But here again we must sharply draw 

 the line between mimicry and oUiterative coloration, because the former, which 

 has played so small a part in the orders we have already considered, is among 

 caterpillars both common and highly developed, almost outweighing in im- 

 portance the other principle, with which it is in many cases intricately com- 

 bined and interwoven. Mimicry, then, does not attempt to render a creature 

 invisible as an actual, well-defined object, but causes him to appear, either 

 wholly or in part, to be something else than what he really-is. The resem- 

 blance of edible or harmless to inedible or noxious creatures for defensive, and 

 to some degree the reverse for offensive purposes, constitutes one of the sim- 

 plest and most generally recognized forms of mimicry, and one to which 

 naturalists have given much attention. Another sort, more to our present 

 purpose, consists in the resemblance of the unobliterated forms of single crea- 

 tures to single well-defined details of their natural environment. This last 

 principle is sometimes, notably in the case of certain caterpillars, altered and 

 elaborated into what may be called compound mimicry. This consists in the 

 imitation, by the surface-aspect of a single creature or part of a creature, 0/ 

 more than one absolute detail of the environment, — which details, owing to their 

 lack of an underlying obliterative shading, still appear to occupy exactly the 

 position of the actual creature. The principles of obliterative coloration, on 



184 



