From green spherical eggs there emerged larvæ 6.5 millimeters in length
without any markings. They were of a light greenish-white, the large
head and long caudal horn being of the same colour. The posterior
boundary of the segments appears as a light shining ring (Pl. VI. Fig.
55).
The characteristic markings of the genus appear on the following day
without the occurrence of any moult: seven oblique white stripes arise
from near the dorsal line, and extend along the sides in a direction
parallel to that of the horn. On the three front segments they are
represented only by three small white spots (Fig. 56). The caterpillar
likewise possesses a marking of which the adult species of the genus
retain only a trace, viz., a well-developed, pure white subdorsal line,
which is crossed by the six anterior oblique stripes, and uniting with
the upper part of the seventh extends to the caudal horn.
I long believed that the markings described were first acquired in
the second stage, as I was possessed with the generally accepted idea
that the changes of form and colour in insects could only occur at the
period of ecdysis. I at first thought that the moult had escaped my
notice, and I was only undeceived by close observation of individual
specimens.
_Second Stage._
The first moult took place after five days, the larvæ being 1.4
centimeters in length. Only unimportant changes of marking are
connected therewith. The subdorsal line loses much in thickness and
definition, and the first and last of the oblique stripes become
considerably broader than the intermediate ones (Fig. 57). The green
ground colour and also the stripes acquire a yellowish hue.
On the other hand, there occur changes in form. The head, which was at
first rounded, becomes of the characteristic triangular shape, with the
apex upwards, common to all the species of the genus, and at the same
time acquires two white lines, which unite above at the apex of the
angle. The shagreening of the skin now also takes place, and the red
spot at the base of the horn is formed.
There appears to be at this stage a general tendency for the suffusion
of red, the thoracic legs also becoming of this colour.
_Third Stage._
The second moult occurs after six or eight days, the marking only
changing to the extent of the subdorsal line becoming still more
indistinct. This line can now only be distinctly recognized on the
three front segments in a few individuals, whilst in the majority it is
completely absent. Sometimes the ferruginous red spots on the oblique
stripes now appear, but this character is not completely developed till
the fifth stage. Out of about ninety bred specimens in which I followed
the entire development, only one possessed such spots, and these were
situated on both sides of the sixth segment.
_Fourth Stage._
The third moult, which takes place after another period of six days, is
not associated with any change of marking.
In this stage also I observed in one specimen (not the one just
mentioned) the ferruginous spots, and again only on the sixth segment.
On account of the theoretical conclusions which may be drawn from this
localization of the spots--supposing it to be of general occurrence--it
becomes of importance to institute observations with different broods,
so as to investigate their first appearance, frequency, and local
limitation. It appears to me very probable that, with respect to
frequency and time of appearance, there would be great differences,
since, in the last stage, it is just this character which shows a great
variability. It would be more remarkable if it should be established
that the first appearance of the spots was always limited to a certain
segment; and there would then be a great analogy with the first
appearance of the eye-spots in _Chærocampa_ and the ring-spots in
_Deilephila_.
_Fifth Stage._
The adult caterpillar does not differ in marking to any considerable
extent from the preceding stages. The first and last stripes do not
appear larger than the intermediate ones, as the latter now increase
in size. Many specimens were entirely without red spots; in others
they were present, but were small and inconspicuous, whilst in others
again there were two spots, one above the other, of a vivid ferruginous
red, these coalescing in some cases, and thus forming one spot of a
considerable size. I have never seen these spots formed into a regular,
linear, coloured border to the white oblique stripes--as occasionally
happens in _Tiliæ_--either in living specimens, blown larvæ, or in
figures.