the other hand, work together to render the creature's actual surface unrecog- 

 nizable as the surface of any object or objects of the immediate foreground, 

 causing it to pass for an empty space through which the background is seen. 



Not being entomologists, we know little or nothing about these larvae from 

 the standpoint of nomenclature and scientific classification. We have taken 

 them as we found them, valued them according to our recognition of their 

 various devices of protective coloration, and classified them, for our own par- 

 ticular purpose, according to these devices. In most cases we do not know 

 more than one stage of a caterpillar, and it is possible or even probable that 

 younger (or older) stages of almost any one of our most interesting specimens 

 may be totally different. Our point has been merely to recognize wonderful 

 cases of protective coloration, and to take them as they stand, for what they 

 are worth. 



Beginning with the large green larvae, such as those of the Luna and Poly- 

 phemus moths, which are disguised purely and simply by counter shading 

 and background-color, aided by a slightly 'mimetic' system of leaf -vein 

 markings and leaf-edge contour, we will trace the gradation of types to the 

 caterpillars whose astoundingly effective disguises are purely mimetic. Such 

 for instance are the larger gray, green, and brown twig-mimicking Geometrce. 

 These larvae, being furnished with bodies whose general shape, color, minute 

 surface-formation, and markings are copied perfectly from the twigs among 

 which they feed, — some of them with forked heads which are exact fac- 

 similes of the buds at the tips of many of these twigs, and others with heads 

 which simulate the truncated ends of dead twigs, — complete the deception by 

 clinging to a stem or branch by the back pair of legs alone, and standing out stiff 

 and straight, absolutely motionless for minutes at a time. But true mimicry 

 in almost all its forms has already been largely and appreciatively studied and 

 described by several naturalists, and we shall therefore devote little more space 

 to it than is necessary to establish clearly in the reader's mind its relation 

 to the other systems of protective coloration among caterpillars. 



Class I. Simple obliterative shading and leaf-color, usually aided by leaf- 



185 



