Although this genus is not admitted into most of the European
catalogues--the solitary European species representing it being
referred to the genus _Sphinx_, Linn.[122]--its separation from
_Sphinx_ appears to me to be justified, not because of the striking
differences presented by the moths, but because the caterpillars,
judging from the little we know of them, likewise show a similar degree
of difference.
I have frequently succeeded in obtaining fertile eggs of _Anceryx
Pinastri_ and I will now give the developmental history of this
caterpillar, which has already been figured with great accuracy in
Ratzeburg’s excellent work on forest insects. Rösel was acquainted
with the fact that the “pine moth” laid its eggs singly on the needles
of the pine in June and July, and he described them as “yellowish,
shining, oval, and of the size of a millet seed.”
On emerging, the caterpillars are six millimeters in length, of a light
yellow colour, the head shining black with a yellow clypeus. The caudal
horn, which is forked at the tip, is also at first yellowish, but soon
becomes black. No particular marking is as yet present, but a reddish
stripe extends along the region of the dorsal vessel, and the course of
the spiracles is also marked by an orange-red line. (Fig. 53, A & B,
Pl. VI.)
As soon as the young larvæ are filled with food they acquire a greenish
streak. The first moult occurs after four days, and immediately after
this there is still an absence of distinct markings, with the exception
of a greenish-white spiracular line. In the course of some hours,
however, the original light green ground-colour becomes darker, and at
the same time a sharp, greenish-white subdorsal line appears, together
with a parallel line extending above the spiracles, which, in _Pterogon
Gorgoniades_, has already been designated as the “supra-spiracular.”
The dorsal line is absent: the head is light green, with two narrow
blackish-brown lines surrounding the clypeus; the horn and thoracic
legs are black; claspers, reddish green; length, twelve to thirteen
millimeters. (Fig. 54.)
_Third Stage._
After another period of four days the second moult occurs, neither
colour nor marking being thereby affected. Only the horn, now no longer
forked, becomes brownish with a black tip. The young caterpillars
are now, as before, admirably adapted to the pine needles, on which
they feed by day, and from which they can only be distinguished with
difficulty.
_Fourth Stage._
The third moult also brings no essential change. The ground-colour and
marking remain the same, only the spiracles, which were formerly dull
yellowish, are now of a vivid brick-red. The horn becomes yellowish-red
at the base.
_Fifth Stage._
The marking is only completely changed in the fifth and last stage.
A broad reddish-brown dorsal line replaces the subdorsal, more or
less completely. The supra-spiracular line also becomes broken up
into numerous short lengths, whilst the green ground-colour in some
specimens becomes more or less replaced by a brownish shade extending
from the back to the sides. Horn, black; the upper part of the first
segment with a corneous plate, similar to that of the _Deilephila_
larvæ.
This stage is very variable, as shown by the figures in various works.
The variations arise on the one hand from the struggle between the
green ground-colour and the reddish-brown extending from above, and,
on the other hand, from a more or less complete disappearance of the
associated longitudinal lines. The latter are sometimes completely
retained, this being the case in a caterpillar figured by Hübner
(_Sphinges_, III., _Legitimæ_ C, b), where both the subdorsal and
supra-spiracular lines are continuous from segment 11 to segment 1, an
instance which may perhaps be regarded as a reversion to the primary
form.
The entire change of the marking from the fourth to the fifth stage
depends upon the fact that the young larvæ resemble the _needles_ of
the pine, whilst the adults are adapted to the _branches_. I shall
return to this later.
The ontogeny of _A. Pinastri_ makes us acquainted with three different
forms of marking: (1) simple coloration without marking; (2) a
marking composed of three pairs of parallel longitudinal lines; (3) a
complicated marking, arising from the breaking up of the last and the
addition of a darker dorsal line.
Of the fourteen species placed by Gray in the genus _Anceryx_, I find,
in addition to the one described, notices of only two caterpillars:--
_A. Coniferarum_,[123] a North American species, lives on _Pinus
Palustris_, and was figured by Abbot and Smith. Colour and marking very
similar to _A. Pinastri_.
_A. Ello_, Linn.,[124] according to the authority of Mérian, is
described by Clemens[125] as dark brown, “with a white dorsal line,
and irregular white spots on the sides.” It lives on a “species of
_Psidium_ or _Guava_.”
Most of the species of _Anceryx_ appear to live on _Coniferæ_, to which
they show a general and decided adaptation. In the absence of decisive
information, I partly infer this from the names, as _Anceryx Juniperi_
(Africa). It has long been known that in our _A. Pinastri_ the mixture
of brown and fir-green, interspersed with conspicuous irregular light
yellowish and white spots, causes the adult larva to present a very
perfect adaptation to its environment. Of this caterpillar Rösel
states:--“After eating it remains motionless, and is then difficult
to see, because it is of the same colour as its food, since its brown
dorsal line has almost the colour of the pine twigs; and who is not
familiar with the fact that beneath the green needles there is also
much yellow to be found?”
This adaptation to the needles and twigs obviously explains why this
caterpillar in the adult condition is so far removed from those of the
genus _Sphinx_, while the moths are so nearly related that they were
only separated as a distinct genus when we became acquainted with a
large number of species.