HEXAPODA. 
57 
This hardening of the body-wall is not continuous, but 
takes place in a series of more or less regular, ring-like bands, 
which give the well-known seg¬ 
mented appearance characteristic of 
insects, and the animals closely Fig. 68.—a Larva, 
allied to them. Between the hardened ring-like segments 
the body-wall remains soft and flexible. In this way provi¬ 
sion is made fcr the various motions of 
the body. The ring-like nature of the 
segments of the body is best seen in 
larvae (Fig. 68), and in the hinder part of 
an adult insect (Fig. 69). The movements 
of the legs, antennae* and certain other 
appendages are provided for in the same 
way; each one is a cylinder made up of 
several segments, and between these seg¬ 
ments the wall of the cylinder remains 
flexible. 
When a single segment of the body is 
examined, the hardened portion is not 
found to be a continuous ring, but is seen 
to be made up of several portions more 
Fig. 69.-A Mole Cricket, or less movable upon each other. Such 
a hardened portion of the body-wall is termed a sclerite 
(scle'rite). 
The sclerites constitute the greater part of the body-wall, 
the soft membranous portions separating them being in 
most cases narrow. Usually these narrow portions are 
mere lines; they are then called sutures (sut urs). 
Frequently the sutures become entirely effaced. We 
are therefore often unable to distinguish certain sclerites in 
one species of insect which we know to exist in another. 
In such cases the effaced sutures are said to be obsolete. 
If the central portion or thorax of an adult insect be 
examined, numerous sclerites and sutures can be observed 
(Fig. 70). 
