June 21 , 1924 
Morphology of the Honeybee Larva 
1179 
The suboesophageal and the terminal, or 8th, abdominal ganglia are, as al¬ 
ready mentioned, compound ganglia. The threefold nature of the suboesopha¬ 
geal ganglion is evident in sagittal sections such as that represented in Plate 3, A. 
At first glance four segments appear to be indicated by the presence of four 
commissures and four corresponding groups of ganglion cells. Examination of 
other sections of this series, however, as well as of the sagittal sections of other 
larvae of the same age, and also of younger larvae, shows that the last two 
bundles of transverse nerve fibers, together with the last two cell groups, belong 
to the labial segment. This component of the suboesophageal ganglion shows 
from the first two well-defined transverse commissures, like those of the succeed¬ 
ing trunk ganglia (86, fig. 45), while the mandibular and maxillary divisions 
never show clearly more than one. In the terminal ganglion three double 
commissures are distinguishable, being those of the 8th, 9th, and 10th abdominal 
segments (38). The same condition is found in embryos of Forficula ( 1 4, fig . 44) • 
One detail in the cellular composition of the nervous system should be noted. 
In the peripheral region of the brain and ganglia of the ventral cord of mature 
larvae are to be seen here and there cells of large size, which in their mode of 
division and other characters are plainly to be identified as neuroblasts. This 
observation corresponds with those of Bauer (&) on the larvae of Vespa, Formica, 
and other insects. Hilton (15) also reports the presence of neuroblasts in the 
brain and ventral cord of the larva of Corydalis. 
CORPORA ALLATA 
The corpora or so-called “ganglia” allata have, as is now well known, no 
intimate connection or relation with the nervous system, but since they have 
also no connection with other organ systems it is convenient to follow the time- 
honored custom of considering them at this point. They have in the mature 
larva the same structures and relations as in the newly hatched larva (36). 
They are spherical bodies (PI. 2, B, Cor All), about 0.85 mm. in diameter, situated 
one on each side of the mid-line, close behind the brain, lying on the dorsal side 
of the anterior arms of the tentorium, near their posterior ends, and in close 
contact with the lateral walls of the aorta. Each is composed of a compact 
mass of polyhedral cells having finely granular and deep-staining cytoplasm, 
and nuclei with abundant chromatin in the form of subspherical granules. Sur¬ 
rounding the corpora is a delicate membrane secreted by the outer layer of cells. 
Just cephalad of the corpora, on each side of the aorta, is a tuft of tracheoles. 
Two or three of these enter the corpora allata and may be seen here and there 
between the cells of the latter. 
TRACHEAL SYSTEM 
The external openings of the tracheal system, the spiracles (fig. 2, A, PI. 1, D, 
Sp), are 20 in number, or 10 pairs, each of the 10 segments from the 2d trunk 
(thoracic) segment to the 10th (8th abdominal), inclusive, bearing one pair. 
They are arranged on each side in a row parallel with the long axis of the body, 
and very nearly midway between the ventral and dorsal mid-lines. The mesotho- 
racic spiracles are placed near the anterior limits of that segment; in the older 
larvae they are located so far cephalad that they have frequently the appearance 
of coming within the limits of the prothorax. The spiracles of the succeeding 
segments are also located near the anterior borders of their respective segments 
at the bottom of shallow depressions, which are continuous with the adjacent 
intersegmental constrictions. Each spiracle is a minute, round aperture situated 
in the middle of a small circular elevation of the surface, the stigma. The 
spiracles are connected by short branches, the spiracular branches (PI. 3, D, 
