I am familiar with numerous specimens in various stages, collected in Sardinia by Dr. Staudinger, and preserved by inflation.
The first stage is blackish, and shows no kind of marking; thus agreeing with the corresponding stage of Euphorbiæ. The second stage is unfortunately not represented in Staudinger’s collection.
The third stage shows a row of ring-spots, which are, however, connected by a very distinct and sharply defined subdorsal line. In the fourth stage a second row of (under) ring-spots is added, whilst the subdorsal line generally at the same time disappears.
The caterpillar remains unchanged during the fifth stage, when it shows a great resemblance in marking to Euphorbiæ; neither does it appear to differ essentially from this species in colour, so far as can be judged from preserved specimens and single figures (in Duponchel and Hübner). I have, moreover, seen several larvæ in the last stage, and the subdorsal could be distinctly recognized as a broad light stripe.
Of the four groups, the second (that of Galii), appears to me to be of but very little importance, as I shall now proceed to show from the development of D. Vespertilio.
Deilephila Vespertilio, Fabricius.
Hitherto I have unfortunately been unable to obtain fertile eggs of this species, so that I can say nothing about the first stage. The latter would have been of interest, not only because of the marking, but also because of the presence of a residual caudal horn.
I am likewise only acquainted with the end of the second stage, having found, at the end of June 1873, a single caterpillar on Epilobium Rosmarinifolium, just previous to its second ecdysis. In the case of such young caterpillars, however, the new characters which appear in the succeeding stage are generally perceptible through the transparent chitinous skin at the end of the preceding stage, so that the markings of the insect are thus caused to change. The caterpillar found was about 16 millimeters long, and of a beautiful smooth and shining grass-green ([Fig. 13]). A broad white subdorsal line extended from the first to the penultimate segment, from which the horn was completely absent. On close inspection the first traces of the ring-spots could be detected near the anterior edge of each segment as feeble, round, yellow, ill-defined spots, situated on the subdorsal line itself ([Fig. 13]). On the first segment only there is no spot, and here no ring-spot is afterwards formed. Besides these markings, there was only to be seen a yellowish-white spiracular line.
This solitary specimen unfortunately buried itself before the moult for which it had prepared itself had occurred; but this ecdysis is associated with a very important transformation. This statement is founded on a blown specimen in Staudinger’s collection; it is only 18 millimeters in length, but already shows the later grey colouring in place of the beautiful green. In this, the third stage, the broad white subdorsal line bears on each segment a red spot enclosed between black crescents above and below ([Fig. 49 A]). In the fourth stage, during which I have seen many living caterpillars, the subdorsal line is still distinctly present in some individuals ([Fig. 14]), but the spots (“mirrors”) are now completely surrounded by a narrow black ring (“ground-area”), which sharply separates them from the subdorsal line ([Fig. 49 B]). In the fifth stage this ring becomes a somewhat irregularly formed black “ground-area,” whilst the subdorsal line completely vanishes ([Figs. 51 and 49 C]). The mirrors are white, but generally have a reddish nucleus, which obviously corresponds to the primary yellow spots from which the whole development of the ring-spots originates. This character is, however, sometimes absent; and many other variations also occur in the earlier stages, all of which can be easily explained as cases of arrested, or retarded development. Thus, the subdorsal line often disappears earlier, and is only present in the fourth stage as a feeble light stripe.