1174 
Journal of Agricultural Research v 0 i. xxvm, no. 12 
indicates, a double one, and near its point of origin it divides into its component 
parts, the frontal nerve (Pl. 1, B and C, FtNv), which turns mesiad to unite with 
the stomatogastric or frontal ganglion ( FtGng ), and the labral nerve ( LmNv). 
The latter takes a cephalad course, entering the clypeus at its extreme lateral 
border, and runs close under the hypodermis to the tip of the labrum, where 
it divides into several branches innervating the hypodermis. 
The two halves of the tritocerebrum are united by the suboesophageal com¬ 
missure ( SoeCom ), a relatively thick strand of nerve tissue which forms a loop 
below the oesophagus. Its two ends are joined to the two halves of the trito¬ 
cerebrum on their ventral sides, just anterior to the crura cerebri. 
In the imago of the honeybee two other pairs of nerves have been described 
which, however, appear to be absent in the larva. These are the tritocerebral 
nerve, discovered by Janet (19) in the ant Lasius, which issues from the inner 
faces of the tritocerebral lobes and innervates the inferior dilator muscles of the 
pharynx, and the salivary nerve (Kenyon, 25), which also issues from the trito¬ 
cerebrum and innervates the salivary gland, Jonescu (21) has shown that the 
roots of both of these nerves lie in the suboesophageal ganglion. 
The suboesophageal ganglion (PI. 1, B and C, 2, B, and 3, A, SoeGng) is len¬ 
ticular in form, somewhat broader at its anterior end, and turned obliquely 
with respect to the long axis of the larva, its anterior end being directed dorsad 
as well as cephalad to meet the crura cerebri. It gives rise to four pairs of nerves, 
as follows: 
1. The mandibular nerves (PI. 1, B and C, MdNv). These arise from the 
antero-lateral angles of the ganglion, just below the crura cerebri. Each of these 
nerves pursues a cephalad course, turning slightly dorsad and laterad, just 
below and parallel to the anterior arms of the tentorium, to the base of the man¬ 
dible, where it divides into branches which are distributed to this appendage. 
2. The maxillary nerves (PI. 1, B and C, MxNv). These arise from the ven- 
tro-lateral face of the ganglion, a short distance behind the mandibular nerves. 
These nerves run ventrad, laterad, and cephalad to the anterior surface of the 
depressors of the maxillae (see p. 1190). Here each of these nerves divides into 
three branches, one of which supplies the depressor, a second the flexor of the 
maxilla, while the third pursues a cephalad course into the interior of the maxilla, 
where it branches among the mesoderm cells situated there. 
3. The labial nerves (PI. 1, B and C, LbNv). These arise from the ventral 
face of the suboesophageal ganglion, near its lateral borders, and about two- 
thirds of its length from the anterior end. Each of these nerves runs ventrad 
and laterad to the major retractor, where each nerve divides into two branches, 
one of which supplies the retractor muscle while the other continues cephalad to 
the tip of the labium.. 
4. X nerves of Jonescu (PI. 1, C, x). These arise from the lateral faces of the 
ganglion close to its posterior end. Although taking their rise from prominent 
papillate elevations on the side of the ganglion, these nerves in old larvae are 
excessively slender and correspondingly difficult to trace. The evidence obtained 
by examination of several series of sections seems, however, to indicate that the 
X nerves pursue a fairly direct course ventrad and laterad, reaching the hypo¬ 
dermis close to the origin of the major retractors of the labium. In sections of 
recently hatched larvae these nerves are relatively much larger than in older 
larvae and in fact are very easily distinguished. Their course is directly laterad 
to the ventral margin of the junction of the posterior arms of the tentorium with 
the hypodermis of the neck region. No indication of a connection with the silk 
gland was seen. It appears therefore that in the bee larva this nerve is purely 
sensory. Jonescu (21) has described this nerve in his account of the brain of the 
imaginal honeybee, but is silent regarding its course and destination. The 
