12 TRANSFORMATIONS OF INSECTS. 
branous space is to be observed on either side of the body between 
them. Moreover, each arch is formed of two side halves, and 
there is often a very distinct line of separation to be noticed 
between the portions of the arches, and also a mark which occu- 
pies this position on the head and along every segment of the 
body of the grub or caterpillar. This middle or median line is 
well seen in the immature Calosoma sycophanta. (See page 15.) 
The segments of the abdomen, which are not provided with 
true legs, appear to be at first nine in number, and there are 
some larvz which have twelve or more of them. Now, on com- 
paring the segments of the larva, chrysalis, and perfect insect of 
the same species, it is noticed that the changes in the form of the 
CHRYSALIS OF Sphimx ligustrt. 
insect are not brought about by an alteration in the consistence 
of the integuments only, but by a diminution in the number of 
the rings or segments. It is true that this diminution is rather 
deceptive in its appearance, for there has not been any fading 
away of the segments, but really a union and a consolidation of 
several in one or more single and separate pieces. Thus it is not 
uncommon for the first rings of the abdomen to become united 
to the last segment of the thorax or body, or for several of them 
to conjoin and leave very faint traces of their former distinctness. 
Take as an example a kind of lepidopterous insect—a moth— 
whose metamorphosis, so far as regards the shape of the caterpillar 
and perfect insect is less than is usual. The large A¢éacus pavonia 
mor is admirably adapted for our purpose. 
The abdomen of the caterpillar commences at the fourth seg- 
ment of the body, as in all other insects, and is formed of nine nearly 
equal rings; the last but one is, however, shorter than the others, 
