254 Annals Entomological Society of America [Vol. V, 
are practically of the same size thoughout their length. How- 
ever, the cephalic end from the metathoracic region to the point 
of attachment to the spinneret is much smaller and serves 
probably only as a conducting tube. These conducting tubes 
can be traced into the head until they reach the chitinous 
projections on the caudal margin of the head, around which they 
bend at right angles and unite on the meson. Farther than this 
the duct was not traced. As one traces, caudad from the 
metathoracic region, a silk gland proper, one sees the beginning 
of the coiled or rather convoluted portion of this organ. Within 
the fifth and sixth abdominal segments the convolutions are 
most abundant. The gland terminates in the mass of Mal- 
phigian tubules and adipose tissue within the seventh abdom- 
inal segment. 
SALIVARY GLANDS. 
The two salivary glands (Fig. 7, s/) appear as delicate, white, 
nodulated, twisted tubes on each side of the pharynx and 
cesophagus. They extend from the anterior portion of the head 
to the region of the metathorax and here end within a flattened 
mass of adipose tissue on the ventral wall of the thorax marking 
the line of division between the mesothorax and the metathorax. 
Tracing a gland into the head, it follows along the space between 
the muscles and the lateral margin of the pharynx to the margin 
of the tendon of the adductor muscle of the mandible, where 
it becomes much reduced in size. 
RESPIRATORY SYSTEM. 
In the discussion of external anatomy, it was noted that 
there were nine spiracles, eight of which were abdominal and 
one thoracic. Opening a larva from the ventral side and 
removing the alimentary canal and a part of the adipose tissue, 
a system of more or less transparent, white, smooth tubes, 
similar to Fig. 11, reveals itself. To follow the trachez with 
most satisfactory results, one should open a freshly killed larva 
and immerse the same in water. In this case the tubes would 
be filled with air and appear as glistening, silver cords. 
Arising from each spiracle, there is an immense, bush-like 
mass of trachee, that branch into many fine tubes, which in 
most cases extend to the various parts, such as muscles, nerves, 
alimentary canal, legs, heart, etc., of the same body segment. 
This holds true of the abdominal segments only. All the 
