278 THE CANADIAN ENTOMOLOGIST 



"M. g.", bifurcating cephalad, which lies upon and innervates the glandular 

 area of the outer part of the mentum. 



The Ventral Nerve of the subesophageal ganglion passes to a lateral ganglion 

 lying in front of the first spiracle, which in turn innervates the muscles 

 of that region and sends two strands to the silk gland of its side. The ganglion 

 is connected with a nerve plexus lying among the main tracheal branches, inter- 

 woven with a string of gland-like cells, oenocytes, and many tracheal threads. 

 This plexus is in turn connected with the cephalic branch of the bracheal nerve. 



The Commissures. 



The Suboesophageal Commissure arises from the brain in conjunction with 

 the Crura Cerebri. It soon separates from the latter and passing ventrad 

 and somewhat cephalad forms a complete loop around the oesophagus. Near 

 the middle line below the oesophagus it gives two or more pairs of delicate fibres 

 to pharyngeal muscles. It is a rather stout cord and must have some function 

 other than these small branches would indicate. It assists greatly in holding 

 the brain in position and that is probably its chief use. 



The Crura Cerebri proceed from each side of the brain downward and 

 backward to connect with the suboesophageal ganglion below the oesophagus. 

 They are unbranched. 



The First Thoracic Ganglion, Pl.X, Fig. 9; PI. XI, Fig. 2, gives rise to two pairs 

 nerves. The smaller, superficial pair, "A," PI. XI, Fig. 2, probably represent the 

 nerves of the connectives between this ganglion and the suboesophageal ganglion; 

 they innervate chiefly the superficial muscles, with threads to the hypoderm, 

 passing across the tracheae eventually to the dorsal muscles and integument. 

 The second pair, the Brachial Nerves, "B", divide each into a cephalic and a 

 caudal division. The former innervates muscles in the base of the head, by the 

 recurrent branch, and the anterior part of the prothoracic segment, and is 

 connected with the superficial nerve. An important branch, "5", from the 

 base of the cephalic division passes into the leg. The posterior division gives 

 a branch, "3", innervating numerous muscles, and then. "4", passes directly into 

 the leg. 



The Third Thoracic Ganglion. The arrangement of the nerves from the 

 second and third thoracic ganglia are illustrated in PI. XI, Fig. 5. The Superficial 

 Nerve, "A", passes outward beneath the recti muscles giving many branches 

 to muscles, tracheae and integument. It has two or three connections with 

 the anterioi branch of the median nerve of its side. The Brachial Nerve, "B", 

 passes directly to the base of the leg and theie gives three branches from a 

 more or less distinct coxal ganglion. The cephalic division, "1", innervates 

 deep muscles and the integument, giving a stout strand, "5", to the leg. The 

 remaining two branches "3" and "4 ', represent the caudal division described 

 for the first thoracic ganglion. Nerve "3" goes to muscles and integument 

 of the caudal part of the segment, and nerve "4" goes to the leg. Nerves "1" 

 and "3" lie below nerve "A". 



The First Abdominal Ganglion, PI. XI, Fig. H. This ganglion gives rise to two 

 pairs of nerves; the anterior, "A", evidently represents the primitive lateral 

 nerve of the connective which has migrated caudad and become fused with the 

 degenerate brachial nerve, and the posterior, "C", is possibly the posterior 



