Jassidce of Illinois. 11 



The vertex is sometimes inflexecl over the front edge of 

 the head, and sometimes does not reach it. 



In front of or below the vertex, and often not distinctly 

 separable from it, the face extends as a long median piece upon 

 the front, often presenting somewhat the shape of an inverted 

 pear. The upper end varies in shape and position with the size 

 and shape of the vertex. The clypeus is a piece attached to 

 the lower end of the face. It varies much in shape, being round, 

 square, expanded at base or at apex, or constricted at the mid- 

 dle or near the base. On either side of the clypeus is a more 

 or less elongate piece, the lora, which also covers a portion 

 of the face; the inner margin is quite straight, and the outer, 

 curved and sometimes constricted at its upper end. 



The remaining portion of the cheeks consists of broad ex- 

 jianded pieces, which may for convenience be divided into two 

 parts, — one forming a somewhat elevated plane or ridge above 

 the antennae and entirely in front of the eyes, and the other 

 being on a lower plane than the rest of the front. The outer 

 edge of this lower portion of the cheeks is variable, being some- 

 times bent outward, sometimes inward, but always forming a 

 thin sharp edge. 



The eyes are somewhat oval organs, situated at the upper 

 posterior corners of the head. They are finely granulate. On 

 the anterior edge, near the antenna?, there is in some species, a 

 considerable notch; otherwise the margin is entire. 



Of even more importance, from a systematic point of view, 

 are the ocelli. These are small round organs often situated on 

 low elevations. In position they are constant in their varia- 

 tion, and therefore of the highest value for classification. Their 

 normal position seems to be at the junction of the vertex, 

 front, and cheeks. In the Tettigonina3 they are on the middle 

 of the vertex; in Acocephalini, just before the eyes, on the 

 front edge of the head; in AUygus, and its allies, on the face, — 

 etc. 



The antennae of Jassidae ( PI. I., Fig. -t ) are almost unif ormh' 

 setaceous; the basal joint is very large, rounded, about as wide as 

 long; the second is much smaller, but still quite large, and of 

 nearly the same shape; the third is as much smaller than the 

 second as the second is smaller than the first, being smallest at 



