June 21, 1924 
Morphology of the Honeybee Larva 
1169 
trunk by nearly its entire width, a sharp and narrow constriction representing 
the neck region. Normally the head is retracted into the pro thoracic segment, 
thus forming a deep fold between the two. The ventral third of the head, 
including the labium, maxillae, and that part of the head capsule to which they 
are attached, is sharply separated from the remainder of the head, which con¬ 
stitutes the head capsule {26), by a deep furrow which extends on each side 
from between the bases of the mandibles and maxillae to the posterior limits 
of the head. This may be conveniently designated as the lateral furrow . 4 Its 
posterior end, on each side, is continuous with the lumen of the posterior arms 
of the tentorium {2Ten). In face view the head capsule is seen to be divided 
dorsally into two equal lobes by a median cleft (PI. 1, F). On the convex 
surface of each of these lobes is a small rounded elevation {Ant), representing 
the distal end of the antennal rudiments. Springing from the head capsule in 
the mid-line, between the antennal rudiments and directed cephalad and ventrad 
is the cushion-shaped common rudiment of the labrum and clypeus {Clp+Lm). 
Its distal end is free from the head capsule and its tip slightly indented in the 
mid-line. 
In Ve^pa, according to Kirmayer {26), the labrum is distinguishable from the 
clypeus, but apparently this is not always possible, since the two areas are repre¬ 
sented as distinct in Kirmayer’s figure 30, but not in his figures 28 and 29. In 
the bee larva they are not always readily distinguishable on the exterior, but in 
many preparations of the head of advanced larvae the rudiment of the clypeus 
and labrum is seen to be crossed by a delicate and distinct fold, dividing it into 
a distal and a proximal part, which can only be labrum and clypeus, respectively 
(PI. 1, F). These two parts are also evidently indicated by the arrangements 
of the muscles. (PI. 6, C.) 
Beneath the labrum is the mouth opening ( Mth ), on each side of which are the 
conical mandibles ( Md ), curved in such a way that their pointed tips lie beneath 
the labrum. The maxillse ( Mx ), which are attached to the ventral part of the 
head capsule, are situated somewhat farther apart than the mandibles. They 
are also longer and of larger diameter, converging a trifle toward the mid-line, 
cylindrical in form, slightly tapering toward their apices, which are rounded and 
tipped each with a small spine. The labium {Lb), which springs from the ventral 
part of the head in the mid-line, is of relatively large size, projecting beyond the 
other mouth parts, bluntly conical in form, rounded at the apex, on which is a 
transversely elongated elevation bearing the slit-like common opening of the 
silk glands ( SlkDO ). On each side of the latter, and slightly ventrad to it, is a 
small spine, similar to those on the maxillae. The upper surface of the labium is 
separated from the lower surface of the labrum by a narrow cleft, forming the 
mouth opening {Mth) which is bounded laterally by the mandibles and maxillae. 
All of the mouth parts are soft and fleshy and covered only by thin chitin, with, 
of course, the exception of the small spines already mentioned. 
Above the common rudiment of the clypeus and labrum, on each side of the 
mid-line, a shallow depression is found. These depressions represent the in¬ 
sertions of muscles on the inner surface of the head capsule. Above each of the 
antennal rudiments is a smaller but somewhat more sharply marked triangular 
depression; these also mark points where muscles are inserted. 
4 A study of the figure by Kirmayer ( 26 ) of the head of the wasp at different stages makes it evident 
that the “lateral furrow 0 of the wasp larva corresponds very closely with the margins of the fossa of the 
proboscis in the imago and this of course must be also true in the honeybee. It would appear, therefore, 
that the ventral part of the larval head lying between the two lateral furrows becomes later differentiated 
into the various structures included in the fossa of the proboscis—mentum, submentum, cardines, etc., 
and also that part of the occipital region ventrad to the foramen. 
