20 THE INSECT WORLD. 
described by anatomists under the name of brain. “This expres- 
sion,” says M. Lacordaire, “‘ would be apt to mislead the reader, 
as it would induce him to suppose the existence of a concentration 
of faculties to assemble the feelings and excite the movements, 
which is not the case.”* The same naturalist observes, ‘‘ All the 
ganglions of the ventral chain are endowed with nearly the same 
properties, and represent each other uniformly.” 
The ganglion situated above the esophagus gives rise to the 
optic nerves, which are the most considerable of all those of the 
body, and to the nerves of the antenne. The ganglion beneath 
the cesophagus provides the nerves of the mandibles, of the jaws, 
and of the lower lip. The three pairs of ganglions which follow 
those placed immediately below the cesophagus, belong to the 
three segments of the thorax, and give rise to the nerves of the 
feet and wings. They are in general more voluminous than the 
following pairs, which occupy the abdomen. 
Fig. 15 represents the nervous system of the Carabus auratus : 
Ais the cephalic ganglion; B, the sub-csophagian ganglion; c, 
the prothoracic ganglion; D and & are the ganglions of the meso- 
thorax and metathorax. The remainder, F F, are the abdominal 
ganglions. 
Before finishing these preliminary observations, it is necessary 
to say that the preceding remarks only apply absolutely to insects 
arrived at the perfect state. It is important to make this remark, 
as insects, before arriving at that state, pass through various other 
stages. These stages are often so different from each other, that 
it would be difficult to imagine that they are only modifications 
of the same animal; one would suppose that they were as many 
different kinds of animals, if there was not abundant proof of the 
contrary. 
The successive stages through which an insect passes are four 
in number: the egg; the larva; the pupa, nymph, or chrysalis ; 
and the perfect insect, or imago. 
The egg state, which is common to them, as to all other articu- 
late animals, it is unnecessary to explain. Nearly all insects lay 
eggs, though some few are viviparous. There often exists in the 
extremity of the abdomen of the female a peculiar organ, called 
* Introduction 4 1’Entomologie, tome ii. p. 192. S8vo. Paris. 1838. 
