June 21, 1924 
Morphology of the Honeybee Lama 
1185 
epipharyngeal fold, which, by drawing together the two edges of the fold, force 
the epipharynx down into the lumen of the pharynx and thus occlude it, while 
the levators, on the other hand, virtually serve as dilators. A larger pair of 
muscles having their origin on the dorsal wall of the labrum are inserted on the 
oesophagus at the lateral margins of the epipharynx, the levators of .the pharynx 
(PI. 4, C, LevPhy). Just ectad of these are inserted still another pair of muscles 
which are attached to the cranial wall on each side of the base of the labrum, 
the superior dilators of the pharynx (PI. 4, C, SDilPhy). On the ventral side 
of the pharynx is a group of muscles having their origin on the anterior face 
of the central body of the tentorium, which are inserted on the ventral wall 
of the pharynx. These are the inferior dilators of the pharynx (PI. 3, A, 
DilPhy ). This list comprises the total equipment of muscles possessed by the 
pharynx. 
The pharynx passes without material change in caliber into the oesophagus. 
This is a cylindrical tube, its walls continuous with those of the pharynx, but 
formed of cells of a somewhat different character, these being much less crowded 
than those of the pharynx and varying in form from cuboid to long columnar. 
Their central ends are rounded instead of flat. This epithelial layer, however, 
does not always form a true hollow cylinder, being generally more or less in¬ 
folded at the sides, top and bottom, and the cells being higher at these points, so 
that the lumen of the oesophagus is frequently quadrangular in section (PL 2 A, 
Oe), or even in some cases rosette-shaped. A chitinous cuticle, continuous with 
that covering the external surface, lines the oesophagus as well as the mouth and 
pharynx. In the anterior part of the fore-intestine this corresponds in thickness 
with the external cuticle, but toward the posterior end of the fore-intestine it 
becomes thinner, and in sections has a much wrinkled and torn appearance. It 
usually extends a short distance into the lumen of the mid-intestine, forming 
the ‘Tunnel” (Trichter) of Schneider (.££). On its external surface the oesopha¬ 
gus is clothed with a single layer of circular (transverse) muscle fibers. Longi¬ 
tudinal muscle fibers appear to be virtually absent. The caudal end of the 
oesophagus, where it joins the anterior end of the mid-intestine, is reflected back 
on itself to form an oesophageal v&lve (PI. 3, A and 5, C, OeVlv) similar to that 
found in many other insects. The cells of that part of the valve which is re¬ 
flected back are notable for their attenuated, almost linear form. Muscle cells 
are lacking between the two folds of the valve. 
The mid-intestine (PI. 4, A, Mint) has the form of a long hollow cylinder with 
rounded ends, and in mature larvae has a diameter about one-third of that of 
the body. It extends from the prothorax to the ninth abdominal segment. It 
is hardly necessary to state that structurally the mid-intestine is a blind sac, the 
posterior end being completely closed. It is anchored in place by numerous 
tracheae which extend mesiad from the longitudinal trunks. The finer branches 
of these tracheae terminate in tracheal end cells upon reaching the surface of the 
mid-intestine. From these end cells numerous tracheoles are sent out envelop¬ 
ing the external surface of the mid-intestine. If the muscular coat of the intes¬ 
tine be stripped off, as can be done in favorable cases, its surface is seen to be 
closely and uniformly dotted with tracheal end cells, one of which is represented 
in Plate 5, D, TraECl. 
The walls of the mid-intestine are composed of a thick single-layered epithe¬ 
lium covered externally by a delicate meshwork of muscle fibers. The cells com¬ 
posing the epithelium (with the exception of a few cells around the anterior end, 
next to the oesophageal valve) are all alike, being relatively large and having in 
general a short and rather cubical form, their mesial margins, however, being 
slightly convex (PI. 5, B). Here and there are to be seen cells which are pyri¬ 
form, with their larger ends directed centrad and projecting into the lumen. 
