320 Studies in the Theory of Descent. 



Besides among the Sphingince, oblique stripes 

 occur in the larvae of certain butterflies, viz. 

 Apatura Iris, Ilia, and Clytie, all of which live on 

 forest trees (aspen and willows), and are excellently 

 adapted to the leaves by their green colour. In 

 addition to these, I am acquainted with the larvae 

 of some few moths, viz. of Aglia Tau and 

 Endromis Versicolora, both of which also live on 

 forest trees. 



Oblique stripes also occasionally occur in the 

 smaller caterpillars of Notice, Geometry, and 

 even in those of certain Pyrales, in all of which 

 they are shorter and differently arranged. In 

 these cases also, my theory of adaptation holds 

 good, but it would take us too far if I attempted 

 to go more closely into them. I will here only 

 mention the extraordinary adaptation shown by 

 the caterpillar of Eriopus Pteridis. This little 

 Noctuid lives on Pteris Aqiiilina ; it possesses 

 the same green colour as this fern, and has double 

 oblique white stripes crossing at a sharp angle on 

 each segment, these resembling the lines of sort of 

 the fern-frond so closely, that the insect is very 

 difficult to perceive. 



After all these illustrations it can no longer 

 remain doubtful that the oblique stripes of the 

 Spkingida are adaptive. But how are the 

 coloured edges bordering these stripes in so many 

 species to be explained ? 



I must confess that I long doubted the possi- 



