266 Annals Entomological Society of America  [Vol. V, 
ganglion. In different specimens examined variations often 
occurred in respect to the exact origin of these nerves. For 
example, it was found that in some cases this second cephalo- 
mesal nerve arose at times ventrad of the caudo-lateral branch, 
while in the majority of cases it arose from the clypeo-labral 
nerve dorsad of the caudo-lateral branch. Further ventrad on 
the clypeo-labral nerves two or three other cephalo-mesal nerves 
project and innervate the cephalic area of the pharynx. 
SYMPATHETIC SYSTEMS OF THE HEAD (Fig. 17 and 18).— 
Two sympathetic systems exist in connection with the supra- 
cespohageal ganglion. The vagus system is an unpaired system 
while the sympathetic system located laterad and dorsad of the 
pharynx is paired. 
Vagus or Unpaired Sympathetic System (Fig. 17 and 18).— 
The vagus system originates from the ventro-lateral part of the 
supracesophageal ganglion near the clypeo-labral nerve and 
consists of the following parts:— 
Arched Nerves.—The pair of arched nerves (a7) is one of the 
pairs of nerves which arise from the ventro-lateral area of the 
supracesophageal ganglion and project ventrad on each side 
of the head adjacent to and somewhat cephalad of the clypeo- 
labral pair of nerves. They extend a short distance ventrad in 
a curved line then turn mesad and unite on the meson ventrad 
of the supracesophageal ganglion and form a small ganglion. 
Frontal Ganglion.—The enlarged, fused, mesal part of the 
arched nerves is the frontal ganglion (f. g.). It rests on the 
pharynx and is located caudad beneath the mouth-like opening 
of the aorta (Fig. 8). Nerves entrad and dorsad extending 
arise from this ganglion. 
Frontal Nerve-—The nerve extending ventrad from the 
frontal ganglion is the frontal nerve (f.7.). It is very short and 
soon divides into two branches which proceed latero-ventrad 
for a short distance and then turn directly ventrad. At the 
point where they turn ventrad, the second cephalo-mesal 
branch arising from the clypeo-labral nerve fuses with them. 
Recurrent Nerve.—The nerve extending dorsad on the meson 
from the frontal ganglion is the recurrent nerve (7. n.). It 
extends in its dorso-caudal course between the aorta and the 
pharynx and cesophagus (Figs. 8 and 18). As it continues its 
course between these organs, it follows the flexure of the pharynx 
so that it extends caudad as well as dorsad. In its course along 
