June 21,1924 
Morphology of the Honeybee Larva 
1189 
next phase in their development takes place subsequent to capping and is directly- 
correlated with the establishment of communication between the lumina of the 
mid- and hind-intestines, and the consequent evacuation of the feces. This 
takes place some time during the twenty-four hours subsequent to capping, and 
has been treated at length by Rengel (44) • In brief it consists, as shown in 
Plate 6, A and B, in an outpushing (caudad) of the fundus of the mid-intestine, 
that is, of the stalk, into the lumen of tl*e anterior enlarged end of the hind- 
intestine and the subsequent perforation of the stalk and also of the diaphragm 
to form a tubular opening through which the fecal accumulations of the mid¬ 
intestine are forced by contractions of the latter. This mass of feces is omitted 
in Plate 6, B. In larvae of this stage the central ends of the Malpighian tubules 
no longer end blindly, but each now opens into the hind-intestine by a minute 
pore-like aperture. These openings are close to the junction of the mid- and 
hind-intestines, as shown on the left side in Plate 6, B, Mai. The appearance 
of this and other preparations suggests that the central ends of the tubules have 
perforated the diaphragm while at the same time their lumina became extended 
to communicate with that of the hind-intestine. A curious feature of the efferent 
ducts of the Malpighian tubules of this stage is the appearance of structures 
which in fixed preparations resemble motile cilia. That the Malpighian tubules 
are now emptying themselves of their contents is strikingly shown by sections 
of the tubules at points more or less remote from the place of attachment. 
Whereas in sections of mature larvae prior to the establishment of communica¬ 
tion between the mid- and hind-intestines the Malpighian tubules have in general 
the appearance of thin-walled tubular sacs, they now show a much diminished 
caliber and the cells forming the walls are no longer flat, but are cubical in form. 
The accumulation of solid excreta in the blind mid-intestine of the bee larva 
is therefore paralleled by the accumulation of fluid excreta (urates?) in the blind 
Malpighian tubules. Both discharge their accumulations at the same time. 
The advantage of this in the life history of the larvae is obvious. 
The imaginal Malpighian tubules appear just previous to capping (PI. 6, A and 
B, mal), as outgrowths of the anterior enlarged section of the hind-intestine ( 1 ). 
SILK GLANDS 
The silk glands comprise a pair of slender cylindrical tubules, thrown into 
numerous short convolutions, and extending from the posterior border of the 
mesothoracic segment to the neighborhood of the sixth abdominal segment (PI. 
4, A, SlhGl). Their location, relative to the other organs, is shown by Plate 5, 
A, SlkGl. They lie, one on each side of the mid-line, closely surrounded by fat 
cells, about halfway between the mid-intestine and the ventral body wall. At 
about the posterior margin of the mesothoracic segment the glands, strictly 
speaking, terminate, and each gland here opens cephalad into a thin-walled duct 
which pursues a straight course into the head, passing close to the ventral wall 
and beneath the suboesophageal ganglion, where it meets its mate from the 
opposite side. The two ducts unite to form a common duct (PL 2, A, SlkD ) 
which terminates on the tip of the labrum. The common duct is cylindrical 
with the exception of its anterior end, where it rather suddenly widens out 
laterally and opens by a narrow transverse slit on an elevation, also transversely 
elongated, situated on the tip of the labrum (PI. 1, F, and 3, A, SlkDO). 
The finer structure of the silk glands is illustrated by Plate 5, F and G. Plate 
5, F, represents an oblique transverse section through one of the silk glands near 
its posterior end. The cells forming the wall of the tube are in many respects 
similar to those forming the mid-intestinal epithelium, although much smaller, 
the nuclei of the walls of the silk gland having a diameter scarcely more than a 
