The Structure and Special Physiology of Insects 23 



wings and legs and the complex thoracic muscular system, while from 

 the abdominal ganglia are innervated the abdominal muscles and sting, 

 ovipositor, or male claspers. In addition to this main or ventral nervous 

 system there is a small and considerably varying sympathetic system (Figs. 

 46 and 48) to which belong a few minute ganglia sending nerves to those 

 viscera which act automatically or by reflexes, as the alimentary canal and 

 heart. This sympathetic system is connected with the central or principal 



FIG. 46. FIG. 47. 



FIG. 46. Brain, circumoesophageal commissures, and subcesophageal ganglion of the 

 red-legged locust, Melanoplus jemur-rubrum. oc., ocellus; op.n., optic nerve; a.n., 

 antennal nerve; m.oc., middle ocellus; op. I., optic lobe; a.l., olfactory lobe; a.s.g., 

 anterior sympathetic ganglion; p.s.g., posterior sympathetic ganglion; f.g., frontal 

 sympathetic ganglion; Ibr., nerve to labrum; oe.c., circumcesophageal commissure; 

 g*, suboesophageal ganglion; md., nerve to mandible; mx., nerve to maxilla; /.., 

 nerve to labium; n., unknown nerve, perhaps salivary. (After Burgess; greatly 

 magnified.) 



FIG. 47. Cross-section of brain, cesophagus, circumcesophageal commissures, and 

 suboesophageal ganglion of larva of the giant crane-fly, Holorusia rubiginosa. 



nervous system by commissures which meet the brain just at the origin 

 from it of the circumcesophageal commissures. 



The specialization of the ventral nerve-chain is always of the nature of 

 a concentration, and especially cephalization of its ganglia (Figs. 49 and 

 50). The abdominal ganglia may be fused into two or three or even into 

 one compound ganglion; or indeed all of them may migrate forward and 

 fuse with the hindmost thoracic ganglion, thus leaving the whole abdomen 



