The North American _Pterogon Gauræ_ and _P. Abboti_[116] also show markings precisely similar to those of this European species in the adult state; but in the two former the markings are of special interest as indicating the manner in which the primary Sphinx-marking has become transformed into that of the apparently totally different adult _P. Œnotheræ_. _P. Gauræ_ is green, with a complicated latticed marking, which closer observation shows to arise from the dorsal line being resolved into small black dots, whilst the subdorsal line is broken up into black, white-bordered triangles. This caterpillar therefore gives fresh support to the remarkable phenomenon that the animals as well as the plants of North America are phyletically older than the European fauna and flora, a view which also appeared similarly confirmed by _Deilephila Lineata_, the representative form of _D. Livornica_. In entire accordance with this is the fact that the larva of _P. Gauræ_ is without the eye-spot on the eleventh segment, and instead thereof still shows the original although small caudal horn. The perfect insect also resembles our _P. Œnotheræ_ in colour and marking, but not in the form of the wings. That the caterpillars of the genus _Pterogon_ originally possessed the caudal horn we learn from _P. Gorgoniades_, Hübn.,[117] a species now inhabiting south-east Russia, and for a knowledge of which I am indebted to Dr. Staudinger’s collection. There are in this about eight blown specimens, from 3.7 to 3.9 centimeters in length, which show a marking, sometimes on a red and sometimes on a green ground, which unites this species with the young form of _P. Œnotheræ_, viz., a broad white subdorsal line, extending from the small caudal horn to the head. In addition to this, however, the caterpillar possesses an extraordinarily broad white red-bordered infra-spiracular line, a fine white dorsal stripe, and a similar line between the subdorsal and spiracular, _i.e._ a supra-spiracular line. The caterpillars in Staudinger’s collection, notwithstanding their small size, all belong to the last stage, as the moth itself does not measure more than 2.6 centimeters in expanse, and is therefore among the smallest of the known _Sphingidæ_. This species has therefore in the adult condition a marking very similar to that of _Œnotheræ_ when young--it bears to _Œnotheræ_ the same relationship that _Deilephila Hippophaës_ does to _D. Euphorbiæ_, only in the present case the interval between the two species is greater. _Gorgoniades_ is obviously a phyletically older species, as we perceive from the marking and from the possession of a horn. We certainly do not yet know whether _Œnotheræ_ possesses a horn in its earliest stages, although in all probability it does so; in any case the ancestor of _Œnotheræ_ had a horn, since the closely allied _P. Gauræ_ now possesses one.