PROTECTIVE RESEMBLANCES IN LEPIDOFTERA 39 



An analogous effect is produced by the larva of a 

 Saw-fly (a plant-eating Hymenopterous insect), which 

 rests stretched along the edge of a leaf. In this posi- 

 tion the larva (Nematus curtispina) would be detected 

 if it covered the notched edge of the leaf ; it has, how- 

 ever, the habit of resting along the curved edge of the 

 gap made by its own exertions. From the side its 

 green ground colour is alone apparent, and it is very 

 difficult to detect. When, however, the leaf is looked 

 at edgeways, it would seem that the larva must be con- 

 spicuous, because its thickness is much greater than 

 that of a leaf. From this point of view the back of 

 the larva is, of course, seen; along 

 the middle line the tubular heart is 



more distinct than usual because of FIG. 11. The larva of 



Nematus curtispina ; 



the transparent skin. The green must stage ; natural 

 blood within makes the heart appear 

 as a fine dark line against a white border on each 

 side, which is entirely due to an accumulation of fat 

 beneath the skin. The white band with the fine dark 

 line down its middle produces the effect of the edge of 

 the leaf, while the rest of the body on each side is 

 green, shaded with dark pigment so as to appear much 

 flatter than it really is. The appearance of the larva 

 is shown in fig. 11. 



The case is also of special interest, because the 

 colouring is chiefly derived from internal tissues or 

 organs showing through a transparent skin. The 

 ground colour is due to the green fluids of the body 



