Of the _Sphinginæ_ living on plants with ordinary foliage, not a single species is without oblique stripes. I am acquainted with ten species of caterpillars and their respective food-plants, viz. _Sphinx Carolina_, _Convolvuli_, _Quinquemaculata_, _Prini_, _Drupiferarum_, _Ligustri_; _Macrosila Rustica_ and _Cingulata_; _Dolba Hylæus_ and _Acherontia Atropos_. Besides among the _Sphinginæ_, oblique stripes occur in the larvæ 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 larvæ 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 _Noctuæ_, _Geometræ_, 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 Aquilina_; 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 _sori_ 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 _Sphingidæ_ 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 possibility of being able to ascribe any biological value to this character, which appeared to me only conspicuous, and not protective. Cases may actually occur in which the brightly coloured edges of the oblique stripes make the caterpillar conspicuous--just in the same manner as any marking may bring about a conspicuous appearance by presenting a striking contrast of colour. I am acquainted with no such instance, however. As a rule, in all well-adapted caterpillars, considering their colour in its totality, this is certainly not the case. The coloured edges, on the contrary, enhance the deceptive appearance by representing the oblique shadows cast by the ribs on the under-side of the leaf; all these caterpillars rest underneath the leaves, and never on the upper surface.