20 THE INSECT WOBLD. 



described by anatomists under the name of brain. " This ex- 

 pression," says M. Lacordaire, " would be apt to mislead the 

 reader, as it would induce him to suppose the existence of a concen- 

 tration of faculties to assemble the feelings and excite the move- 

 ments, 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 oesophagus gives rise to 

 the optic nerves, which are the most considerable of all those of 

 the body, and to the nerves of the antennae. The ganglion 

 beneath the oesophagus 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 oesophagus, 

 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 ; 

 A is the cephalic ganglion ; B, the sub-oesophagian ganglion ; c, 

 the prothoracic ganglion ; D and E 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 a 1'Entomologie, tome ii. p. 192. In 8vo. Paris. 1838. 



