106 Psyche [June 
As these unions of the pharynx and the efferent canal with the 
setze must be more or less loose to allow for the forward and back- 
ward sliding movements of the setz, as they are used in feeding, 
the membranous sheath must fit tightly in and about these parts 
to insure that there be no leakage at these two joints. 
The tentorial structures are variously modified. The middle 
region of the ventral plate of the pharynx is supported by two 
chitinous plates which abut against and are attached to the pos- 
terior portion of the head in the gula region. These pass forward . 
and upward as broad curved narrowing plates. They converge as 
they approach the pharynx and their inner edges turn up so that 
the ventral surfaces of the turned up portion lie along the sides of 
the ventral plate and are united by tendons to the ventral plate 
of the pharynx, see Pl. 1 f. 4 and 7. These plates continue for- 
ward along the sides of the pharynx, their ventral surfaces extend 
further up the side of the pharynx. In cross section they appear 
somewhat crescent shaped as seen in PI. 1 f. 6 (t). Lying on either 
side of the pharynx, they form a trough or bed in which the pharynx 
lies. Anteriorly the salivary pump lies below the pharynx and 
between these curved tentorial structures securely held in place 
by the connective tissue which surrounds it. Just anterior to 
the pump, portions of the two inner surfaces of the plates pass 
upward on either side of the efferent canal supporting it and con- 
tinue with it to its connection with the sete. A portion of each 
plate passes forward and slightly downward, fusing medianly, 
with that of the other side, below the portions which support the 
efferent canal to form the plate to which is attached the dorsal 
anterior surface of the labium. 
Opposite the anterior end of the salivary pump, the outer mar- 
gins of the plates roll upward and over the fused central plates, 
and form the two black heavily chitinized horns of the tentorium 
(ht), each of which contains a groove, which acts as a guide to the 
converging sete, which meet over the tip of these horns and pass 
forward together above the lobes of the clypeus. 
The horns of the tentorium separate posteriorly to allow the 
chitinized tip of the efferent canal and its supporting structures 
to pass upward between them and connect with the salivary canal 
in the maxillary sete at the point where the setz come together. 
The lateral margins of the horns of the tentorium and the lateral 
margins of the plate to which the anterior dorsal surface of the 
