Of the North African D. Mauritanica, which likewise belongs to the Galii group, I have not been able to obtain specimens or figures of the younger stages. The adult caterpillar is very similar to that of Euphorbiæ, but differs in the absence of the second row of ring-spots. For this reason it must be regarded as a retarded form at an older stage of phyletic development.
I now proceed to the Livornica group.
Deilephila Livornica, Esper.
This, the only European species here to be considered, possesses almost the same markings as Galii in its fourth stage, i.e., a subdorsal line with interpolated ring-spots. The species is known to be rare, and I have not been able to obtain living specimens, but I have examined several blown larvæ, all of which agree in having the ring-spots sharply distinct from the whitish subdorsal line, so that the latter is thereby interrupted. Figures of the adult larva are given in the works of Hübner, Boisduval, and Duponchel. In most specimens the ground-colour is brown, although Boisduval[93] also figures a light green specimen; from which it may be inferred, from analogy with Galii and Vespertilio, that the first stages are green. In Dr. Staudinger’s collection there is a young larva, probably in the fourth stage, the ground-colour of which is light ash-grey. The dorsal and subdorsal lines are white, the latter showing in the positions where the ring-spots subsequently appear, small white “mirrors” with red nuclei, exactly corresponding to the stage of Vespertilio represented in Fig. 49 A, [Pl. VI]. The “mirrors” are nothing more than dilatations of the subdorsal line, which is not therefore interrupted by them. The black “ground-area” does not surround the “mirrors” completely, but borders them only above and below, and is much more strongly developed above, extending in this direction to the dorsal line.
The fourth group comprises the two species D. Lineata, Fabr., and D. Zygophylli, Ochs., the former being the North American representative of our D. Livornica, but differing in remaining permanently at the fourth stage of this last species. I am acquainted with D. Lineata only through the figure of the adult larva given by Abbot and Smith, which figure, judging from the position and form of the spots, I am compelled to believe is not quite correct, notwithstanding the excellence of the other illustrations. The ground-colour of the caterpillar is green; the subdorsal yellow, bordered with black, slightly curved, arched lines, which nowhere interrupt its continuity. This North American species appears therefore to be an older form than our Livornica.
Deilephila Zygophylli, Ochsenheimer.
This species, which is the next allied form to D. Lineata, is an inhabitant of Southern Russia. I have seen four specimens of the caterpillar in Dr. Staudinger’s collection, three of which are certainly in the last ontogenetic stage. The ground-colour appears ash-grey, ash-brown, or blackish with whitish granulations. A broad white subdorsal line extends to the base of the black caudal horn, this line in one specimen appearing at first sight not to possess a trace of spot rudiments ([Fig. 50]). On closer investigation, however, there could be observed, in the same position where the ring-spots stand in the other species of Deilephila, small black crescents above and below the subdorsal line. In other specimens the white subdorsal line had also become expanded in these positions into distinct spots; indeed, in one individual light white mirror-spots, bordered above and below by black crescents, stood on the subdorsal line ([Fig. 50 A]).
It is thus in this distinguishing character that the caterpillar is extremely variable, and we may suppose either that this species is now in a state of transition to a higher stage of phyletic development, or else that the ring-spots were formerly more strongly developed, and are now degenerating. The developmental history of the larva could alone decide which of these two views is correct. There would be no difficulty in procuring materials for this purpose if one of the numerous and zealous Russian naturalists would take up the subject.
Deilephila Hippophaës, Esper.
This is the only representative of the fifth and oldest group known to me. The moth resembles D. Euphorbiæ to the extent of being sometimes confounded with it, a circumstance which is made the more remarkable by the fact that the caterpillars are so completely different.