THE CANADIAN ENTOMOLOGIST 277 



On one specimen, extremely delicate fibres were distinguished running from 

 the ventral face of the brain to the heart immediately below. There were three, 

 one in the middle and one on each side. Whether these are of nervous or con- 

 nective nature I am unable to say. 



The brain is abundantly supplied with tracheoles from neighbouring 

 tracheae. 



The Siiboesophageal Ganglion. 



PI. X, Fig. 9. 

 The Suboesophageal or Infraoesophageal Ganglion is a large, llattened, 

 somewhat quadrate ganglion, lying in the caudal part of the ventral portion 

 of the head. It is connected with the supraoesophageal ganglion by the Crura 

 Cerebri, as already desciibed. and, b\' a very short commissure, is connected with 

 the first thoracic ganglion, thus becoming the cephalic ganglion of the ventral 

 chain. 



It gives origin to four pairs of nerves. The first three pairs arise from the 

 cephalic part of the ganglion, at the sides, mesad of the ventral origin of the 

 commissures. 



The Mandibular Nerves, Fig. 9. The most anterior pair, the Mandibular 

 Nerves, extend cephalad, more or less parallel with the other two pairs, though 

 usually lateral to them, as far as the ventral condyle of the mandibles. They then 

 turn abruptly and proceed almost directly to the dorsal side of the mandibles in 

 rather close relation with the external branch of the labral. Before reaching the 

 mandible each mandibular nerve bifurcates, the two divisions running nearly 

 parallel to each other. At the entrance to the mandible the cephalic branch enters 

 the mandibular ganglion, which innervates the interior of the mandible, and certain 

 of the mandibular muscles, particularly the retractors (see Fig. 1); while the 

 caudal division proceeds laterad above the ventral condyle and divides into 

 a dorsal and ventral branch. The position of these branches is explained on 

 Fig. 1 . The ventral branch extends to the base of the head to innervate various 

 muscles of that region. 



A delicate branch from the mandibular nerve fuses on the middle line with 

 its fellow from the opposite side, and the two are continued cephalad as a median 

 strand into the hypopharynx, which it innervates. Before reaching the median 

 nerve each of these branches from the mandibular gives rise to a slender thread 

 which joins the plexus of minute threads lying upon the hypoderm below the 

 mouth. 



The Maxillary Nerves, Fig. 9. The second pair, the Maxillary Nerves, 

 extend cephalad nearly parallel with the labial, and bend laterad behind the 

 union of the silk glands to innervate the muscles and sense organs of the maxillae. 



The Labial Nerves, Fig. 9. The third pair, the Labial Nerves, proceed 

 cephalad along the sides of the oesophagus and pharynx to innervate the 

 region of the labium. They seem clearly to innervate muscles and glands and to 

 be directly connected with the cutaneous sympathetic; the branches are illus- 

 trated in the figures. On some specimens there is an unbranched connective 

 uniting the labial nerves behind the fusion of the silk glands. 



Near the union of the silk glands each labial nerve gives a short, thickened 

 branch to the median line. The two branches unite in an elongate ganglion, 



