CHAP. VI.] NERVOUS SYSTEM OF ARTHROPODS. 



103 



would, of course, be of importance to any organisms, but 

 more especially to those possessing active powers of loco- 

 motion. They would serve, on the one hand, to assist in 

 bringing their possessors into relation with food, or with 

 sexual mates, and, on the other, to warn them of the 

 approach of enemies. 



The nervous system of Insects varies not only among 

 different classes and orders, but even in the same indivi- 

 dual in different stages of its development. The cater- 

 pillar of a Moth (fig. 39) or Butterfly presents a nervous 

 system not very different from that met with in the 

 Centipede; while in the imago 

 or perfected Insect, the same 

 system has undergone some re- 

 markable changes there is, for 

 instance, an increased size of 

 the cerebral ganglia, and also a 

 notable development of some of 

 the ganglia pertaining to the 

 ventral cord, while concentra- 

 tion or even suppression of 

 others is met with. 



T T -T-, . FIG. 42. Brain and Adjacent Paitg 



In such insects as Butter- of Nervous Sy&tem of a rat her 



flieS, BeeS, DraffOn-flieS, and &"&&, apterous Beetle, Timarcka 



' tenebricosa. (Newport.) A, Brain re- 



Othei'S Where the Visual Organs ceiving the antennal nerves, and also 



are enormously developed, aad 



in which the pOWer Of vigOrOUS mencement of the oesophageal cords; 



T . . T n . , . . D, the sub-oesophageal ganglia ; 6, the 



and Sustained flight IS COrreS- vaguS) or visce ral nerve before reach- 



pondingly increased, the nerVOUS ing its ganglion; c, lateral visceral 



nerves. 



system as a whole attains its 



maximum of development among the Arthropoda. The 

 brain of these creatures differs from that existing in all 

 other members of the class by reason of the great develop- 



