330 ZOOLOGY 
a slight groove. Each lobe is continued laterally into a stout 
optic nerve, which supplies the compound eyes; besides this it 
gives off a nerve to the antenna of its own side, which branches 
abundantly in the lamelliform segments, and a third nerve to 
the labrum or upper lip. Two short commissures encircle the 
oesophagus, and unite in the sub-oesophageal ganglion, which 
also lies in the head; this ganglion supplies nerves to each of 
the mouth appendages, the mandibles, and first and second 
maxillae. From the sub-oesophageal ganglion two commissures 
pass backward, and enter the first or prothoracic ganglion, 
which gives off nerves to the thoracic muscles and first pair of 
legs. Close behind this is a large ganglionic mass, formed by 
the fusion of the meso- and meta-thoracic ganglia, its double 
origin being shown by a transverse groove (Fig. 188). This 
compound ganglion supplies nerves to both pairs of wings, and 
to the posterior two pairs of legs. 
The abdominal ganglia are all fused into one mass, which 
is withdrawn into the thorax, and lies in the metathorax 
immediately behind the ganglion of that segment; indeed, it 
seems as if part of the abdominal nervous system is absorbed 
into the last-named ganglion, which is said to supply nerves to 
the first abdominal segment ; the remaining seven pairs of nerves 
arise from the abdominal mass, and pass backwards to their 
respective segments, where they split into an anterior and a 
posterior branch. 
In addition to the central nervous system, there is a 
small sympathetic system, which consists of the following 
parts. A pair of fine nerves arise from the supra-oesophageal 
ganglion and fuse in the middle line, and so form a minute 
triangular ganglion lying in the head (Fig. 188); from this 
a median unpaired nerve passes back and forks over the crop, 
and the branches unite into a small ganglion again. There are 
also two pairs of minute ganglia which innervate the heart 
and tracheal system, these are situated just behind the supra- 
oesophageal ganglion. 
Like all other Insects the cockchafer is dioecious, and the 
female may be distinguished from the male by having six 
lamelliform segments in its antennae, whereas the male has 
seven. 
