June 21,1924 
Morphology of the Honeybee Larva, 
1175 
writer has also seen it in sections of material of the imaginal bee, but has been 
unable to follow it to its termination. As in the larva, it is insignificant in size, 
although plainly evident at its point of departure from the ganglion. Janet (18) 
has described a fourth pair of nerves arising from the suboesophageal ganglion in 
the ant Myrmica rubra, and Krauss (28) and Hammar (13) have described a pair 
of nerves in the Corydalis larva arising from the caudo-lateral portion of the 
ganglion just cephalad of the junction of the connectives with the ganglion. In 
Myrmica rubra the nerve corresponding in position to the X nerve, termed by 
Janet “the labial sympathetic nerve (nervus sympatheticus labi) ” gives rise to a 
complex system consisting of a ganglion and three branches on each side of the 
mid-line. These innervate the labial gland and also adjacent muscles and 
tracheae. In Melanoplus (39), Corydalis larva (13), Forficulaand certain other 
insects (29) a pair of nerves make their exit from the lateral faces of the suboeso¬ 
phageal ganglion near its posterior end, generally known as “salivary gland” 
nerves. In the bee larva no connection between the X nerves and the salivary 
(silk) gland could be established, but it nevertheless is possible in view of the 
close correspondence in the point of exit from the suboesophageal ganglion of the 
salivary gland nerves in Melanoplus, Corydalis, etc., the labial sympathetic 
nerves in Lasius, and the X nerves in Apis, that these are all homologous. Piet- 
schker ( 42 ) has described a nerve in the ant which he terms “nervus accessorius. ” 
It springs from the suboesophageal ganglion about half way between the labial 
nerve and the connectives and runs toward the labium, where it ends in depressions 
of the hypodermis, possibly representing sense organs. This nerve in its point 
of exit and its termination closely approximates the X nerve of the bee larva. 
The accessory nerve of Pietschker is entirely distinct from the salivary nerve 
which was also observed and makes its exit from the dorsal side of the ganglion. 
It is also not to be identified with the labial sympathetic nerve of Janet. 
The brain and suboesophageal ganglion of the mature larva, with reference 
to their external form, differ slightly from those of the young larva, and very 
materially from those of the imago. In the newly hatched larva (36) the two 
lobes of the protocerebrum (including the optic lobes), as compared with those 
of the mature larva, are shorter and thicker, and are bent caudad instead of 
lying in a plane transverse to the long axis of the larva. Moreover, they show 
clearly a subdivision into three lobes, as described by Viallanes (49) for Or- 
thoptera. The antennal lobes, although not prominent, are present as distinct 
swellings, while the tritocerebral lobes are scarcely differentiated externally 
from the antennal lobes on the one hand a)ad the thick crura cerebri on the 
other. The latter merge caudad into the elongate suboesophageal ganglion, 
which is divided externally into three swellings representing its three component 
pairs of ganglia. 
As compared with the brain of the larva that of the imago (21) shows striking 
differences. Superficially there is a certain resemblance between the two, 
principally on account of their flat expanded form and the large size of the 
optic lobes. In the imago, however, the protocerebral lobes become high 
bilobed elevations separated from the optic lobes by well marked constrictions, 
and the antennal lobes become conspicuous rounded swellings projecting from 
the anterior face of the brain; while the tritocerebral lobes, which are fairly 
distinct in the larva, become almost indistinguishable. Moreover, in the imago 
the suboesophageal commissure becomes so fused with the suboesophageal 
ganglion as to be indistinguishable externally, while the frontal ganglion sinks 
to insignificant proportions. On the other hand, the suboesophageal ganglion 
of the mature larva differs but little in form, size and general external appearance 
from that of the imago. It is scarcely necessary to remark that most of these 
differences, such as the difference in size of the antennal lobes, may readily be 
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