THE BRAIN OF THE LOCUST. 
223 
CHAPTER XI. 
-ps- 
THE BRAIX OF THE LOCUST. 
In order to appreciate the habits, migratory, reproductive, &c, of the 
locust, and to learn something of its general 
intelligence as an insect and as compared <»- 
with other insects, it is necessary for us to sp. 
study with a good deal of care the organ of 
the locust's mind, i. e., its nervous system, 
comprising its nervous centers aud the nerves if- 
arising from them. The present chapter 
will be devoted to a study of the braiu. 
The nervous system in general. — The ner- 
vous system of the locust has been described 
in a general way in the First Annual Eeport 
of the Commission (p. 2G1, Figs. 14, 15). It 
consists of a series of nerve centers or ganglia, 
connected by nervoiis cords called commis- 
sures. There are ten of these ganglia in the 
locust, i. e., two in the head, the first and 
largest of which is called the "iraira"; there 
are three ganglia in the thorax, and five in 
the hind-body or abdomen. The brain is 
situated in the upper part of the head, rest- 
ing upon the gullet or oesophagus, whence its 
true name stqrracesophageal ganglion. (Plate 
IX, Fig. 1.) The succeeding nerve-center is 
situated in the lower part of the head, be- 
hind the mouth and under the oesophagus, 
hence it is called the subasopliageal ganglion. 
(Plate IX, Fig. 5.) The supracesophageal 
ganglion is larger than the succeeding ones, 
and is compressed from before and behind, 
its height being much greater than its 
length, while the other ganglia are more or 
less lens-shaped and flattened vertically, be- 
ing broader than thick. The brain really is 
a double ganglion, being composed of two 
hemispheres, each hemisphere being a single 
ganglion or nerve-center; all the succeeding 
ganglia are also double ganglia ; but for con- 
venitnce we will call the "brain" and each 
of the succeeding nerve-centers a ganglion. 
Each side of the brain contracts, and then 
swells out into a rounded portion next to Tia - 9 - 
the eye, called the optic ganglion. From this optic ganglion the optic 
