band of leaf-green, which greatly furthers the deception. There are many 

 wonderful caterpillars of this type, usually a good deal larger than the one 

 here shown, which is the only one we have succeeded in painting. 



Class IV. Partial mimicry of a detail of the normal surroundings, with a 

 polished back which under certain conditions reflects the color of surrounding 

 objects, combined with flat-leaf -edge counterfeiting, achieved by light-and- shade 

 gradation. The pretty caterpillar shown in Plate XV, Fig. R (No. i reflecting 

 nothing, No. 2 reflecting green, and No. 3 reflecting red), is our sole example 

 of this class. Its light, extremely shiny back, which serves for shadow-efface- 

 ment when the caterpillar hangs upside down, serves also for actual reflection 

 of the color of the encompassing foliage (as in the white spider shown in Plate 

 XVI, Figs. V-Y), while the yellow stripe down its side must usually pass for 

 the stem of some other poplar leaf than the one on which it is feeding. The 

 fact that this well-pictured stem must, owing to its large size, appear to be at 

 least as near the observer as the caterpillar actually is, allies the case to partial 

 mimicry rather than to simple obliterative coloration. When the caterpillar 

 rests on a yellow stem, rather than a leaf-edge, as it often does, the mimetic 

 element is still more pronounced, for then the stem which he is in fact conceal- 

 ing with his feet is by his yellow stripe made to appear to pass on uninter- 

 ruptedly, if somewhat crookedly, and the remainder of his body merely merges 

 with the general green which surrounds him. This larva we have found only 

 on small-leaved poplar trees. 



Class V. Complete structural mimicry of a common detail of the creature' 's 

 habitual inanimate surroundings. The wonderful little caterpillar which we 

 have chosen to typify this class bears on its back a double row of large fernlike 

 fronds, with perfectly developed stem and branches, and when feeding or 

 resting amidst the curled-up edges of unhealthy maple or other leaves, which 

 it evidently mimics, is almost impossible to detect. In its elaborateness and 

 efficiency, this disguise is among the very most wonderful. At the season 

 when the caterpillar is to be found, most of the forest trees have many of these 

 partially withered leaves. Wherever the creature stands on a leaf, it passes 



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