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



Compound Eyes — The compound eyes (E) occupy the 

 greater part of the dorsal aspect of the head at the sides of the 

 vertex. They are large oval or semicircular bodies, which 

 extend back to the anterior margin of the pronotum. In the 

 immature forms they are relatively larger than in the adult 

 and are more rounded. The character of the facets is the 

 same as that of a generalised insect, although the number of 

 these facets is exceedingly great. 



Movable Parts of the Head. (PI. XX, XXI, Figs. 6,7,13,16,17). 

 Antennos (Figs 18-21). — The antennae (A) are for the most 

 part setaceous in form ; structurally there is very little difference 

 between the morphology of the antennae in the various forms, 

 although it will seem as well to indicate here the more important 

 of these. The number of segments or joints varies considerably 

 and frequently cannot be distinguished at the distal ends. The 

 basal segment and those adjoining it are the most modified 

 in size. In the males of Idiocerus (Bythoscopid^) the distal 

 joints of the antennae are developed into small oval plates, 

 which Hansen has regarded as sensory structures. In many 

 of the Tettigoniellids and Jassids, small hairs or spines are 

 developed on the basal joints of the antennae. The antenna 

 of Deltocephalus inimicus figured shows this structure (Fig. 19). 

 These spines may have some sensory function, although no 

 trace of sense cones were found on them. The antenna are 

 inserted on the face between the compound eyes and the 

 longitudinal suture of the front. In some cases the point of 

 insertion may be a deep cavity, in others it may be shallow. In 

 some of the Bythoscopidae the cavity is overlapped by a distinct 

 ledge. 



Labium — (PI. XX, Figs. 9, 13). The beak or proboscis of 

 the Jassid mouthpart is the labium or lower lip. It is relatively 

 short and thick, circular in outline, and is three-jointed. The 

 distal joint, or tip of the labium is the largest, the proximal 

 the smallest and the middle is about intermediate in size 

 between the two. Externally the labium appears to emerge 

 from under the labrum, but a closer examination w411 reveal 

 the fact that the tip of the epipharynx, a small, peg-like struc- 

 ture, which is attached to the anterior end of the labrum, fits 

 into a narrow groove on the surface of the labium and gives it 

 some means of support in one direction. Ventrally the labium 



