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.