I have treated of the polymorphism of _Stellatarum_ in detail, not only because it has hitherto remained unknown, and an analysis of such cases has been completely ignored,[109] but more particularly because, it appears to me, that important conclusions can be drawn therefrom. Moreover, such an extreme multiplicity of forms is interesting, since, so far as I know, polymorphism to this extent has not been observed in any insect. The theoretical bearing of this polymorphism will be treated of subsequently. It is not in any way connected with a more advanced development of the markings, since _M. Stellatarum_ shows in this respect a very low state of development. This species displays only two stages:--(1), complete absence of all markings; and (2), a simple subdorsal, with dorsal and spiracular lines. We must therefore admit that the phyletic development of the markings has for a long time remained at a standstill, or, what expresses the same thing, that the marking which the adult larva now possesses is extremely old. In order to complete my observations on _M. Stellatarum_, I now add some remarks on the pupa, the colour variations of which it appeared of importance to investigate, owing to the extraordinary variability of the caterpillar. The pupa varies but very slightly; the ochreous yellow ground-colour sometimes passes into reddish, and sometimes into greenish; the rather complicated blackish-brown marking of streaky lines is very constant, especially on the wing portions, being at most only more or less strongly pronounced. The minute colour variations of the pupa therefore have no connection with the colour of the caterpillar, both green and brown larvæ furnishing sometimes reddish-yellow and sometimes greenish-yellow pupæ. The comparison of _M. Stellatarum_ with the other known species of the genus, brings scarcely any addition to our knowledge of the phyletic development. Thus, the two European species of which the caterpillars are known, viz. _M. Fuciformis_ and _Bombyliformis_,[110] show essentially the same markings as _Stellatarum_, the chief element being a well-developed subdorsal line. The Indian _M. Gilia_, Herrich-Schäf., possesses also this line,[111] and, together with the East Indian _M. Corythus_, Walk.,[112] has oblique stripes in addition; the stripes do not, however, cross this line, but commence underneath it, and probably originated at a later period than the subdorsal line. Should this be the case, we must regard _M. Corythus_ as representing a later phyletic stage. According to Duponchel’s figures, in both _M. Fuciformis_ and _Bombyliformis_ small oblique stripes (red) occur near the spiracles, but these have nothing to do with the oblique stripes of _M. Gilia_ just mentioned, as they run in a contrary direction. Of the two European species, I have only seen the living caterpillar of _Fuciformis_, and this possessed no oblique stripes.