From these observations we might venture to expect that in the third stage of Hippophaës, the subdorsal line would also be free from this spot on the eleventh segment, and it is possible that in the second stage this line is itself absent.
The Genus Deilephila: Summary of Facts and Conclusions.
Regarding only the adult larvæ of the species of Deilephila, these represent in their five groups, five stages in the phyletic development of the genus; but if we also take into consideration the developmental history, two more stages must be added, viz., that in which the caterpillar possesses no particular marking, as was found to be the case in the first stage of the development of D. Euphorbiæ and D. Dahlii; and a second stage with a subdorsal line, but without any ring-spot formations. Seven stages of phyletic development must therefore be distinguished.
Stage 1.—No species with entire absence of marking in the adult form now occurs.
Stage 2.—A subdorsal, accompanied by a spiracular line, extends from the caudal horn to the first segment. This also no longer forms the final stage of the ontogeny, but is, however, undoubtedly retained in the second stage of several species (D. Vespertilio, Livornica, Lineata, and perhaps also Galii).
Stage 3.—The subdorsal line bears a ring-spot on the penultimate segment; the other markings as in the last stage. D. Hippophaës only belongs to this stage, a small number of specimens, however, showing a transition to the following stage by the transference of ring-spots from the posterior to the anterior segments.
Stage 4.—Open ring-spots appear on the subdorsal line on all the segments from the eleventh to the first. D. Zygophylli and the North American D. Lineata belong here.
Stage 5.—Closed ring-spots are situated on the subdorsal line. Of the known species, only D. Livornica concludes its development at this phyletic stage.
Stage 6.—A single row of ring-spots replaces the subdorsal line. D. Galii, Vespertilio, and Mauritanica represent this stage at the conclusion of their ontogeny.[95]
Stage 7.—A double row of ring-spots. Only D. Dahlii, Euphorbiæ, and Nicæa attain to this highest stage of Deilephila marking, the two first species in the fourth stage, and Nicæa in the third stage of its ontogeny.