264 Annals Entomological Society of America [Vol. V, 
cords arising from the lateral margins help to complete the circle 
about the pharynx by connecting themselves to the latero- 
caudal portions of the supracesophageal ganglion. 
Mandibular Nerves —Adjacent to the crura cerebri and 
extending in a caudo-mesal direction, there arises a pair of 
nerves (md. 1b. n.), which are of approximately the same size as 
the crura cerebri. These nerves extend ventrad and divide 
into two nerves of unequal size; the larger nerve (md. n.) 
proceeds cephalad and ventrad and innervates the mandible. 
Labial Nerves.—The labial nerves (/b. 1.) arise from the mesal 
side of the mandibular-labia! nerve (md. 1b. n.). They extend 
ventro-caudad and innervate the labium. 
Maxillary Nerves —Caudad and adjacent to the mandibular 
nerves, the maxillary nerves (mx. n.) arise. They are smaller 
and soon branch and innervate the manxille. 
Unidentified Nerves —Caudad and slightly dorsad of the 
maxillary nerves, there arises on each side a nerve of consider- 
ble size (gz), which extends laterad into the muscles of the head 
toward the salivary ducts but I have been unable to determine 
what they innervate. 
Ventral Nerves —From the mid-lateral area of the ganglion, 
the ventral nerves (v) project accompanied by their accustomary 
tracheee. In this ganglion a light stain brings out very success- 
fully the branches of the trachez (¢) as they radiate over the 
surface of the ganglion. The ventral nerves in this case project 
dorso-caudad into the caudal part of the head. 
Supraesophageal Ganglion (Fig. 17 and 18, sp).—The 
supracesophageal ganglion (sp) is the largest ganglion of the 
nervous system and is located on the cephalic surface of the 
pharynx. The transverse diameter of the ganglion is about 
twice that of the ventro-dorsal diameter. The ganglion is 
constricted along the meson into two lobes. The following 
nerves arise from this ganglion :— 
Crura Cerebri—The two large crura cerebri (c. c.) that 
proceed from the subcesophageal ganglion in a dorso-cephalic 
direction, connect with the supracesophageal ganglion on the 
latero-dorsal margins. The two trunks are comparable to the 
commissures that extend between the ganglia 1n other regions of 
the body. Just dorsad of where the crura cerebri arise from the 
supracesophageal ganglion, a large trachea enters the ganglion 
on each side of the head. These trachez, a short distance from 
