HEXAPODA . 
73 
already indicated, consists of a ganglion in the head above the oesoph¬ 
agus, and of a series of ganglia, typically one for each segment of 
the body, lying on the floor of the body cav¬ 
ity, and connected by two longitudinal cords. 
In the head, one of these cords passes on 
each side of the oesophagus, from the brain 
to another ganglion in the head below the 
oesophagus, thus forming a nervous collar 
about the alimentary canal. From each 
ganglion nerves arise, which supply the ad¬ 
jacent parts; and from the thoracic ganglia 
nerves extend to the legs and wings. This 
series of ganglia is really a double one; but 
each pair of ganglia arc more or less closely 
united on the middle line of the body, and 
often appear as a single ganglion. Figure 84 
gives a general view of the nervous system of 
Corydalis cornuta. From the brain (a) two 
large nerves extend to the compound eyes, 
and a smaller pair to the antennae; the sub- 
oesophageal ganglion (/;) supplies the mouth- 
parts with nerves; and each of the thoracic 
and abdominal ganglia supplies its segment 
of the body. 
How Insects Breathe—The Respiratory System .—A common mis¬ 
take made by beginners in the study of Entomology is to suppose 
that insects breathe through the mouth as do the higher animals. 
Many a beginner has carefully poured chloroform on the head of an 
insect in the expectation of killing it in that way, and has been sur¬ 
prised at his poor success. 
The truth is, insects breathe through their sides. If an insect be 
carefully examined, there can be found along the sides of the body a 
series of openings (Fig. 85). These are the openings through which 
Fig. 85.—Side-view of Locust with wings removed. 
the air passes into the respiratory system and are termed spiracles 
(spir'a-cles). 
Fig. 84.—Nervous system of 
Corydalis. (After Leidy.) 
