Plate XIII, Fig. E, shows the larger-spotted species of beech leaf -edge larva, 

 in its normal position. Fig. F shows the smaller-spotted species in position. 

 Figs. G and H show these two larvae inverted, against a black background. 

 Figs. I and J are two sketches of a white-birch leaf-edge larva, I being the 

 creature in situ, and J a simple back view. Of this larva we have seen only 

 two specimens. It is but sUghtly shaded from dark to light, and either lives 

 usually very far in among the leaves, where the light is diffuse, or else, because 

 it feeds on rather stiff leaves, whose edges are but slightly pulled downward 

 by its weight, can make little use of counter shading. The light spots on this 

 caterpillar closely picture the small, transparent worm-scars so common on 

 the leaves of the white birch. 



As we have said, the principles involved in the protective coloration of 

 this group of caterpillars are variously modified. The forms just described 

 are among the commonest and most noteworthy of those we have seen, but they 

 lack one element of finish which is found in caterpillars of another branch of 

 the class. Those already described have backs very slightly indented be- 

 tween the segments, and without humps, hence their contour can never pass 

 for the perfect edge of a leaf which is in any degree serrated, as most leaves are. 

 But as they freely mow away whole sides of leaves, and usually rest close to the 

 stem on the mutilated edge, this is hardly a lack. They merely pass for a con- 

 tinuation of a gnawed and imperfect leaf-edge, in whatever position they cling, 

 except in cases where they are so far from the stem that their backs are 

 farther out than even the unbroken leaf-edge could be — as sometimes when 

 they are beginning a new leaf. In such a case the smooth back-line is, momen- 

 tarily, a defect. (This need hardly be taken into account, however, because 

 it is the habit of these larvae to work in along the midrib of a leaf, from a 

 position on the stem, and it is only in rare cases that their backs are out beyond 

 the line of a normal leaf-edge.) The caterpillars of the other type, of which 

 we have as yet seen only one individual, may be called the contour leaf-edge 

 larvae, for their back-contour is formed in close imitation of the perfect, serrated 

 edges of the leaves on which they feed. This resemblance is effected by a 



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