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.—Brain, circumoesophageal commissures, and suboesophageal 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., circumoesophageal commissure; 
g\ suboesophageal ganglion; md., nerve to mandible; mx., nerve to maxilla; l.n., 
nerve to labium; n., unknown nerve, perhaps salivary. (After Burgess; greatly 
magnified.) 
Fig. 47.—Cross-section of brain, oesophagus, circumoesophageal 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 circumoesophageal 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 
