308 The Ohio Journal of Science [Vol. XVI, No. 7, 



found. These are the maxillary plates (mx. pi.), and they 

 occur in all Homoptera. Although the maxilla are fused with 

 the gense, they can be distinguished from the latter in that 

 they articulate with the maxillary set« (mx. s.), which are 

 enclosed within the head-capsule. The maxillary plates extend 

 around the sides of the face and constitute the border; they 

 completely surround the clypeus and meet anteriorly beneath 

 the labrum, where they are connected by a membrane. At the 

 sides the plates are turned down and under, forming the part 

 of the ventral surface of the head. Distally they turn back 

 on the under side of the head, and develop into two rectangular 

 chitinous plates — with which the maxillary setas articulate. 

 The maxillary setae are attached to these chitinous plates, 

 which in turn are hinged to the body of the tentorium (t. b.). 



The maxillary setae (mx. s.) resemble the setae of other 

 Homoptera; they are long and slender for the most part, but 

 their proximal basal region is swollen, and attaches to a small 

 tendon (t.), which passes dorsally into the retractor muscles 

 (mx. r.) of the setae. A membrane sleeve surrounds the seta, 

 as far as the entrance to the labium. The strong protractor 

 muscles (mx. p.) of the maxillary setae are attached to the maxil- 

 lary plate, while the retractor muscles attach to the head- 

 capsule at the sides of the occiput. The articulation of the 

 seta is on the inner side of the maxillary plate and it can easily 

 be seen by reference to the figure (PI. I, Fig. 7) how the maxillae 

 can be worked forward and backward. 



The exact homology of the maxilla in Homoptera is a ques- 

 tion on which no little discussion has arisen. The amalgamation 

 of the maxillary plate with the genee, would lead one to believe 

 at once that the whole of the plate at that side of the clypeus 

 constitutes the gena, but on examining the internal structure, 

 and the connection of the maxillary plate with the maxillary 

 seta, it can readily be seen that the maxillary seta is intimately 

 connected with the maxillary plate. Added to this the invagi- 

 nations of the posterior arms of the tentorium are to be found 

 at the sides of the occipital foramen, and are adjacent to the 

 attachment of the maxillary plates with their setas. In all the 

 insects so far examined, the invaginations of the posterior arms 

 of the tentorium have always been associated with the point 

 of attachment of the maxilla. 



