The light green eggs are nearly spherical, and after fourteen days
(beginning of July) the young larvæ emerge. These are also of a light
green colour, and are conspicuous for the great length of the caudal
horn, which is nearly half as long as the body. This horn is likewise
of a light green at first, but becomes dark violet in the course of an
hour. No trace of any markings can be detected at this stage.
As soon as the caterpillars are hatched they commence to nibble the
empty egg shells; then they run about with great activity, and after
several hours take up their position on the largest vein on the under
side of the lime leaves, where they remain for a long period. In this
situation they have the same form and colour as the leaf-vein, and
are very difficult to discover, which would not be the case if they
reposed obliquely or transversely to the vein. In about 4-5 days the
caterpillars undergo their first moult, and enter upon the second
stage. On each side of the segments 11-4, there now appear seven
oblique whitish stripes on a somewhat darker green ground; these
slope in the direction of the caudal horn. Owing to the transparency
of the skin, a dark green dorsal line appears in the position of the
underlying dorsal vessel, the green contents of the alimentary canal
being distinctly visible through the absence of adipose matter in the
tissues. The larvæ possess also a fine whitish subdorsal line, which
extends from the horn to the head. The horn at this stage becomes black
with a yellowish red base.
In the third stage, which occurs after six or seven days, the oblique
stripes appear darker, and the subdorsal line disappears.
_Fourth Stage._
After another period of 4-5 days the third moult takes place, and there
now commences a dimorphism which will perhaps be better designated
as variability, since the two extremes are connected by transitional
forms. The majority of the larvæ have, as in the preceding stage, pure
white oblique stripes, but many of them possess a blood-red spot on
the anterior side of the stripes, this spot showing all gradations
in size and depth of colour between maximum development and a mere
trace. Special interest attaches to these spots, as they are the first
rudiments of the coloured border of the oblique stripes which occurs in
so many _Sphinx_ caterpillars.
In the fifth stage--the last of the larval development--the red spots
become more strongly pronounced. Among eighty caterpillars from one
brood there were about twenty without any red whilst the remainder
were ornamented with more or less vivid blood-red spots, often large
and irregular in form. In some specimens the spots had become drawn
out into lines,[98] forming a coloured edge to the oblique white
stripes, similar to that possessed by the larva of _Sphinx Ligustri_.
The caterpillar is thus represented in many figures, but generally
the coloured stripe is made too regular, as in reality it is always
irregularly defined above, and never so sharp and even as in _Sphinx
Ligustri_. The character is here obviously not yet perfected, but is
still in a state of development.