299 



teroptera. In the Ccrcopidac there is often a falsely-suturcd-off 

 antero-median pieee (resembhng somewhat in appcanuicc the 

 Heteropterous fylits) which coalesces posteriorly with the disk 

 of the vertex and anteriorly fuses more or less with the frons, 

 though usually separated by a keel ; whether this is really part of 

 the vertex or is a part of the frons pushed up, is uncertain. In 

 some Fulg^oroidea (most Cixiinae) there are 3 ocelli, two in the 

 usual Fulgoroid position (i. e. at the more or less flat sides of the 

 head, close to the antennae) and one at the anterior margin of 

 the frons, adjoining the clypeus. In the Tetigonioidea they may 

 l)e almost anywhere on the vertex, sometimes close to the base, 

 (Tetigoniinae etc.), sometimes near, or on, the anterior margin 

 of the head (lassinae etc.), sometimes again at the extreme api- 

 cal margin of the vertex, close to the frons (Agalliinae.) In 

 Stenocotinae & Kahavaluinae, they are situated at the bottom of 

 elongate furrows on, or near, the anterior margin of the vertex. 

 Often they are obviously functionless, though rudimentarily 

 present, rarely entirely wanting. The work of the ocelli is 

 enigmatical. In the Fulgoroidea, their position is practically 

 uniform, though their usefulness must be sadly circumscribed by 

 the surrounding elevated keels. It is evident that in the Teti- 

 gonioidea the position of the ocelli is of great importance for 

 systematic purposes — for it is obvious that the directions and 

 extent over which an insect can see, must influence its life ver}- 

 greatly. It is unnecessary to dwell on this subject, but it is 

 evident that the visuality or light perception or whatever their 

 use may be, must i)e very different in Tctii^o)iia where the ocelli 

 are placed on the disk of the vertex, near the base and turning 

 a little outwards, to Agallia where they are far on the disk of 

 the face ; and sufficiently diiferent in Phryuwmorphiis where they 

 are small and flattish and placed on the smooth anterior margin 

 of the vertex, to Aphnnics where they are near the anterior mar- 

 gin (but on the disk,) this genus being carinate anteriorly, the 

 disk being a little sunk. 



In his celebrated studies, Hansen has laid great stress, and 

 rightly so, on the form of the antennae and on the structure of 

 their sensory organs. I much regret that I have not had suffi- 

 cient time to continue Hansen's researches very far, but I have 

 done so sufficiently to convince myself of their great value. 

 Their characteristics in the various super-families etc. are suf- 

 ficiently displayed in Hansen's table, quoted previously. 



Of the Thorax I need not speak, except to point out that 

 while usually of ordinary structure in the Tetigonioidea (with the 



