HEXAPODA. 
67 
cles, through which a waxlike material is excreted : these 
are commonly called honey-tubes ; they are also termed 
cornicles , nectaries, or siphuncles ; see page 157. 
The Internal Anatomy of Insects, 
(For advanced students .) 
As has been shown in the preceding pages, the body-wall serves 
as a skeleton, being hard, and giving support to the other organs of 
the body. This skeleton may be represented, therefore, as a hollow 
cylinder. We have now to consider the arrangement and the general 
form of the organs contained in this cylinder. For the details of the 
structure of th. internal organs the student is referred to more special 
works. 
The accompanying diagram (Fig. 80), which represents a vertical, 
longitudinal section of the body, will enable the student to gain an idea 
of the relative position of some of the more important organs. The 
parts shown in the diagram are as follows: The body-wall,or skeleton 
Fig. 80.—Diagram showing the relation of the internal organs. 
(s); this is made up of a series of overlapping segments ; that part of it 
between the segments is thinner, and is not hardened with chitine, 
thus remaining flexible and allowing for the movements of the body. 
Just within the body-wall, and attached to it, are represented a few of 
the muscles (m ); it will be seen that these muscles are so arranged 
that the contraction of those on the lower side of the body would 
bend it down, while the contraction of those on the opposite side 
would act in the opposite direction. The alimentary canal (a) occu¬ 
pies the centre of the body, and extends from one end to the other. 
The heart (//) is a tube open at both ends, and lying between the 
alimentary canal and the muscles of the back. The central part of 
the nervous system (u) is a series of small masses of nervous matter 
connected by two longitudinal cords: one of these masses, the brain, 
lies in the head above the alimentary canal; the others are situated, 
