Some captured females were at once placed in an enclosure about the
size of a small sitting-room. It was evident that they did not feel
quite at home under these conditions, frequently beating their heads
and wings against the tarlatan, but some of them nevertheless laid eggs
at the base of the leaves of _Euphorbia Cyparissias_. The eggs much
resemble those of _Chærocampa Elpenor_, being spheroidal in form, but
rather smaller, and of a somewhat darker green. They were laid in small
clusters composed sometimes of as many as seven, the single eggs being
placed near together, but never touching, and seldom at the point of
the leaf, but generally near the end of a twig, where young shoots are
in close proximity. During the embryonic development the eggs become
coloured, first yellow and partly blackish, and finally completely
black.
_First Stage._
The young caterpillars (Fig. 37, Pl. V.) immediately after hatching
measure four millimeters in length; they are at first rather light,
but in the course of half-an-hour they are seen by the naked eye to
become of a deep velvety black; later, on increasing in size, they
again become paler, appearing of a greenish-black, and subsequently
blackish-green. On further increasing in size (Fig. 38), they are
blackish-green, with the horn, head, legs, and a crescent-shaped
chitinous plate on the back of the prothorax black. There are also on
the last segment a double and two single black chitinous plates. Of the
later marking of the caterpillar there is scarcely anything present.
The spiracles appear as white spots, and on each segment there are
a number (mostly ten) of small warts, each of which emits a single
bristle.
When the young larvæ have attained a length of seven millimeters they
are olive-green, and do not contrast so brilliantly with the green of
the _Euphorbia_ leaves as before; neither do they as yet possess any
markings.
_Second Stage._
The first ecdysis occurs after five days, and with this there appears
quite suddenly a very complicated pattern. The ground-colour is now a
light yellowish-green (Fig. 39), and on each of the twelve segments,
near the front border, there is a pure white round spot in the
middle of a large black transverse spot. I shall designate these, in
accordance with the nomenclature employed for _Chærocampa_, as the
white “mirrors” on black “ground-areas,” both together constituting
“ring-spots,” as distinguished from “eye-spots” proper, in which a
“nucleus,” the pupil of the eye, is also added. In many, but not in all
specimens, very distinct traces of a subdorsal line can be seen as a
light whitish stripe connecting the white spots. The horn, the thoracic
and prolegs, and some spots on the head, are black.
The caterpillars remain unaltered till after four days, when, having a
length of 17 millimeters, the second moult takes place, bringing with
it changes quite as great as those which occurred with the first.
_Third Stage._
The caterpillar now assumes the shagreened appearance which it
possesses in the adult state. Small white warts are arranged in rows
from the dorsal to the spiracular line, and again underneath this line
on the abdominal legs. These dots are not only of value as a character
for differentiating the genera _Deilephila_ and _Chærocampa_, but they
also play a part in the peculiar spot-marking which will be shown later
on. The ground-colour of the caterpillar is now light green (Fig. 40),
replaced by black on certain parts. From the black “ground-area” of the
ring-spots, two black triangles extend towards the posterior borders of
the segments, but usually without reaching them.
The ring-spots are not essentially changed, although it may be observed
that in most specimens the shagreen-dots under each ring-spot are
somewhat larger, and stand closer together than in other places. In
the following stage they become fused into a second white “mirror,” so
that two ring-spots stand one above the other, their black ground-areas
meeting. The formation of the second ring-spot sometimes takes place in
the present stage (Fig. 42).
The subdorsal line has now completely vanished, whilst the spiracular
line[89] appears as a broad stripe above the legs. The horn is yellow
with a black point, and the black spots on the head have increased in
size.
_Fourth Stage._
The third moult, which again occurs after four days, is not accompanied
by such important changes. The green ground-colour has now completely
disappeared, and is replaced by a dull black. The caterpillars are now,
as also in the previous stage, extremely variable. Thus, for example,
a triangular patch of the green ground-colour may be retained on the
posterior edge of the segments (Fig. 41), those specimens which possess
this character generally having their markings retarded in development,
as shown by the absence of the second “mirror” of the ring-spots.
In Fig. 41 the shagreen-dots from which this second “mirror” is
subsequently formed, are distinctly larger than the others, and on the
eleventh segment two of them have already coalesced.
_Fifth Stage._
After another period of four days, the fourth moult takes place. The
marking remains the same, but the colours become more vivid; the
brick-red of the head, horn, dorsal line and legs, changing into a
fiery red. The spiracular line, formerly green alternating with yellow,
generally becomes resolved into a row of reddish-yellow spots. Ten days
later the caterpillar (8.5 centimeters in length), ceases to feed, and
prepares for pupation.
In this last stage also there is great variability of colour, but
although each particular character is subject to fluctuation, the
individuals of the same brood show but little variation among
themselves.[90] Thus, the dorsal line is sometimes black, and sometimes
red, or again, this colour interrupted with black, so that only small
red spots mark its course. The head may be entirely red, or this
colour mixed with black. On the under side of the caterpillar, red
generally predominates, but in some specimens this is replaced by
black. The ground-colour is also variable, being generally a shining
brownish-black, but sometimes dull coaly black. The shagreen-dots
are sometimes white and sometimes yellow, and the “mirrors” of the
ring-spots are also often yellowish.
The most interesting variation, however, appears to me to be the
following:--In many specimens from Kaiserstuhl (Breisgau), the red
was unusually vivid, and was not limited to the ordinary places, but
occupied also the triangles on the posterior edges of the segments
(Fig. 44), which are green in the third and fourth stages (Fig. 42).
This variety has also been figured by Hübner. In one individual (Fig.
43), the under ring-spots were wanting, whilst the upper ones possessed
a beautiful red nucleus fading away anteriorly, and showing the first
step in the formation of a complete eye-spot.
I cannot positively assert that a fifth moult occurs in the last ten
days, although I am very doubtful whether this is the case. It is
certain, however, that some time before pupation, and whilst the larva
is still feeding, the striking colours fade out, and become replaced
chiefly by black.
The ontogeny of this species is obviously but a very incomplete
representation of its phyletic development. This is at once apparent
from the large gap between the first and second stages. It is not
possible that a row of ring-spots can have arisen suddenly; in all
probability they have been developed from a subdorsal line, which in
_Euphorbiæ_ is now only indicated in the second stage by a faint line.
This conjecture is raised to a certainty when we call in the aid of the
remaining species of _Deilephila_.