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enter into the composition of the pattern: darkbrown and diluted 
yellow. It is true that these colours only maintain themselves in the 
older instars of the larval period, as originally the caterpillar is 
green. So when we should ascribe a general applicability to the 
rule that the colours and markings of the younger stages invariably 
represent more original conditions than those of the later, we should 
be obliged to suppose that the brown colour had arisen from the 
green one. But though this rule can be applied in many cases, it 
by no means may be considered as of universal validity. Especially 
in insects I am of opinion that everywhere the green colour is a 
secondary modification of other shades, which lie farther to the red 
side of the spectrum, as I have already tried to demonstrate in my 
paper on the genus Charagia among Hepialids. 
In convolvuli therefore the change from green to brown should 
be considered as a reversion to more primitive conditions, and in 
connection with this supposition we might regard the green 
colour in ligustri, and to a certain extent also in atropos, 
as due to secondary modification’). Possibly this change in the 
general shade might be brought in connection with the reduction 
of the original design, which on the thorax has led to complete, on 
the abdomen to partial obliteration, and moreover on the latter has 
called forth a greater contrast between the uniformised green ground- 
colour and the very obvious pink and white oblique striae. 
As a hint that in convolvuli the brown caterpillar has best retained 
the original character, we may also regard, that in this species the 
connection of the markings with the every where occurring subdivision 
of the body-segments in a series of eight annuli or subsegments is 
most conspicuous. But likewise in the other two species it is obvious 
that the diagonal striae (pink and white in fgustr, pink and yellow 
in atropos) are composed of a step-like series of dark and light 
blocks of colour. With regard to this feature, those of the firstmen- 
tioned species strike us by the peculiarity, that in the forward 
prolongation of the diagonal striae on the foregoing segment a row 
of three or four white specks occurs, growing smaller from behind 
forward. In this anterior prolongation of the white striae the blending 
of the specks, which enter into their composition, has not yet taken place. 
In the green caterpillar of atropos another proof is seen for the asser- 
tion, that more extensive striae, bands and fields of colour are the result 
of the blending of smaller spots arranged in transverse rows. For 
1) This species also possesses a brown variety of the caterpillar, and this, as well 
as that of convolvuli, shows a more complete and primitive pattern than the 
green one. 
