white line along the sides of the back, terminates then abruptly against the 

 smooth, deep yellow green of the back itself. Thus it appears that the 

 perfect flat-leaf-edge color achieved by counter shading extends over part of 

 the larva, and then suddenly gives place to an entirely contradictory and at 

 first inexplicable stripe of dark, exactly where the culmination of paleness would 

 normally occur. Finding the larva on the ground, one may well be puzzled, 

 but the first sight of it normally situated on a leaf is a revelation, as our picture 

 (Fig. M, i) shows. The counter-shaded blue-green belly and sides repre- 

 sent an extension of the upper side of the leaf, the white line is an intensified 

 representation of the line of the leaf-edge, and the sharply contrasted and 

 deeply shadowed yellow-green back simulates perfectly the shadowed under- 

 side of a leaf, either the same one or one slightly more distant. If we examine 

 the caterpillar very closely, we discover still another wonderful detail of its 

 disguise. The dark-green back itself is slightly counter shaded to escape all 

 trace of a solid appearance, and to match perfectly the monochrome under surface 

 of leaves. A narrow yellow line runs along the middle of the back, and this 

 serves to efface the culmination of shadow which would otherwise appear 

 there. In the case of this leaf -edge larva the green back doubtless often passes 

 for the underside of the same leaf, as shown in the picture (Fig. M, i), 

 but in that of certain larger caterpillars which wear a similar device, as for 

 instance the larva of the common smaller hog-nosed woodbine caterpillar, the 

 illusion is less exact; and as this caterpillar rests on a stem rather than a leaf- 

 edge, even its light patch often passes for a portion of some partially concealed 

 leaf, rather than for the continuation of a wholly exposed one. 



The modifications and different adaptations of these various principles 

 are almost unlimited, and we can only hope to give examples of a very few 

 most highly representative and easily comprehensible forms. Fig. M gives 

 three representations of the beech larva just described, i being the larva in 

 position on the leaf-edge, 2 the same detached from the leaf, and 3 a simple 

 back-view of the creature. These caterpillars are usually unspotted, as here 

 shown, but are sometimes marked with brown patches closely resembling 



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