The case is similar with the spot-markings. I have already shown that under certain conditions ring-spots may assume the exact appearance of eye-spots by the formation of a nucleus in the “mirror,” such as occurs occasionally in _Deilephila Euphorbiæ_ (Fig. 43), more frequently in _D. Galii_, and as a rule in _D. Vespertilio_. Nevertheless, these markings arise in quite another manner to the eye-spots of the _Chærocampinæ_, with which they consequently have no genetic relation; the two genera became separated at a time when they neither possessed spot-markings. Further, in _Pterogon Œnotheræ_ we find a third kind of spot-marking, which is most closely allied to the ocelli of the _Chærocampa_-larvæ, but is situated in quite another position, and must have originated in another manner, and consequently quite independently of these eye-spots. It can also be readily understood why the first and second elements of the markings of the _Sphingidæ_ should be mutually exclusive, and not the second and third or the first and third. A light longitudinal line cutting the oblique stripes, considerably diminishes that resemblance to a leaf towards which the latter have a tendency, and it is therefore only found in cases where an adaptive marking can be of no effect on account of the small size of the caterpillar, _i.e._ in quite young stages. (See, for instance, Fig. 56, the first stage of _S. Populi_.) At a later period of life the old marking must give way to the new, and we accordingly find that the subdorsal line vanishes from all the segments on which oblique stripes are situated, and is only retained on the anterior segments where the latter are wanting. In some few cases both elements of marking certainly occur together, such as in _Calymnia Panopus_ and _Macroglossa Corythus_; but the oblique stripes are, under these circumstances, shorter, and do not extend above the subdorsal line, and in _Darapsa Chœrilus_ even become fused into the latter.[166] In certain cases there may also be a special leaf structure imitated by the longitudinal lines, but on the whole the latter diminish the effect of the oblique stripes; and we accordingly find that not only has the subdorsal disappeared from those segments with oblique stripes, but that most larvæ with this last character are also without the otherwise broad spiracular and dorsal lines. This is the case with all the species of _Smerinthus_[167] known to me, as well as with all the species of the genera _Sphinx_, _Dolba_, and _Acherontia_.