760 Wisconsin Academy of Sciences, Arts , and Letters. 
lateral margins. Over the upper surface are a number of 
slightly curved setae which exceed in length those on cor¬ 
responding parts of the epipharynx. The entire basal part 
of the hypopharynx is borne on a chitinous prop which arches 
up over the reservoirs of the salivary glands. At the inner 
margin of the hypopharynx, just at the opening into the pha¬ 
rynx, there is a transverse plate of thickened chitin (fig. 7, Ph. 
pi.) which, in a sagittal section shows as a tooth (fig. 8, Ph. 
pi.) ; this is used to hold open the entrance into the aliment¬ 
ary canal, there being at this region a dorso-ventral compres¬ 
sion. Directly in front of this opening the cuticular layer is, 
on both roof and floor, slightly thicker than over the rest of 
the surface; the cuticula here is transparent and slightly rugose. 
Excepting those parts mentioned the cuticular lining of the 
mouth shows but slight variations in thickness although over 
the floor it is a little thinner than on the roof. 
Alimenteky Caxal. 
General (fig. 9). At its commencement the oesophagus is 
a narrow tube which changes but little in diameter through 
the head and cervical region. It at first passes upwards and 
forwards (the latter direction is but slight and assumes the 
head to be in a deflexed position), the slight forward direc¬ 
tion soon changes and the oesophagus gradually turns back¬ 
ward to pass under the supra-oesophageal ganglion. Just be¬ 
fore passing out of the head through the occipital foramen it 
assumes a position which is parallel to the longitudinal axis 
of the insect’s body; this position relative to the body it re¬ 
tains to the anal opening. The anterior portion of the oeso¬ 
phagus is the thinnest part of the alimentary canal. Just 
after leaving the cervical region the oesophagus commences to 
increase in diameter, this increase continues through the pro¬ 
thorax and becomes greater at the anterior end of the meso- 
thorax. At the beginning of the mesothorax this increase in 
diameter appears, from a dorsal view, to be very gradual; 
from a lateral view the change is seen to be an abrupt one. In 
