June 21, 1924 
Morphology of the Honeybee Larva 
1171 
cavities) on either side of the labrum. They are directed cephalad and slightly 
mesiad, their smaller ends directed outward, and are attached by the mesial side 
of their larger inner ends to the head capsule on the mesial side of the peripodal 
cavities. The long axis of the rudiments is therefore actually bent through an 
angle of about 90 degrees (PI. 2, D). The cavities themselves are closed only by 
the chitinous cuticle, which is continuous over their external openings. The tips 
of the antennal rudiments project slightly above the general surface of the head 
and produce the small rounded elevations visible from the exterior (PI. 1, F and G, 
Ant). The segments of the antennae are indicated by the wavy contour of 
their hypodermis as well as by the distribution of the antennal nerve. (PI. 2, D, 
AntNv.) 
The leg rudiments (fig. 1 and 4, A, 1L-3L) are short fusiform or ovoid in shape, 
like the antennae, and are also situated in deep open depressions covered externally 
only by the cuticle. The leg rudiments are directed caudad and mesiad. The 
segments of the imaginal legs are indicated by annular constrictions. The wing 
rudiments are fiat hollow outgrowths of the hypodermis of the mesothoracic and 
metathoracic segments and are situated in shallow depressions low down on these 
segments, close to the ventral surface and at a considerable distance ventrad to 
the stigmata of these segments (fig. 1, PI. 1, D, and fig. 4, A, WngR). In outline 
the wing rudiments are heart-shaped. 
The rudiments of the genitalia (fig. 1, 1G-SG) are six in number, one pair being 
situated on the sternite of the 8th abdominal segment and two pairs on the 9th 
abdominal segment, as described by Dewitz ( 9 ). At this stage they are small 
knob-like outgrowths situated in open depressions. 
While the cuticle of the trunk is thin and elastic, that covering the cranium 
is much thicker and forms a more or less rigid capsule for the protection of the 
contained brain and other organs. The chitin covering the mouth parts is, as 
has already been said, thin and relatively flexible. 
The rigidity of the head capsule is further increased by the cra»nial endoskeleton 
or tentorium, formed during the embryonic period by invaginations of the 
ectoderm (36). In the imagoes of insects the tentorium is evident as a frame¬ 
work of chitinous bars, but in the bee larva the embryonic conditions persist so 
that the tentorium consists of tubular ingrowths of the hypodermis lined with 
chitin, the hypodermal portion being relatively well developed as compared with 
the imago, in which the hypodermis forms a relatively insignificant layer. Lying 
between the oesophagus and the suboesophageal ganglion, transverse to the long 
axis, is a wide tube lined with a thick layer of chitin, compressed in a dorsoventral 
direction and slightly curved, the convex side being directed cephalad. This 
tube is subdivided—on embryological evidence—into three nearly equal parts, a 
central body (PI. 1, A, and 6, D, Ten), and two lateral arms, the ‘‘posterior” 
arms (2Ten). The latter become continuous with the walls of the head capsule 
at the posterior ends of the deep lateral furrows of the head. These infoldings, 
or at least their posterior part, may in fact be considered as the expanded distal 
ends of the posterior arms, the furrows leading at their posterior ends directly into 
the lumen of the posterior arms, which, together with the lumen of the central 
body, forms a continuous open passageway from one side of the head to the other. 
At the junction of the central body with the lateral arms arise the anterior arms 
(PI. 1, A, 1 Ten) which extend cephalad and dorsad to the anterior wall of the 
head capsule, with which they are united. These points of junction are marked on 
the exterior by two minute pits, situated above the bases of the mandible at the 
sides of the labrum (PL 1, F, ITen). The anterior arms are also tubular but are 
much more slender than the posterior arms and are round in section. Halfway 
between their anterior and posterior ends each of the anterior arms gives off a 
