36 The University Science Bulletin. 



STRUCTURAL CHARACTERISTICS. 



The outstanding characteristic of the membracids is their re- 

 markably developed pronotum. This sclerite is usually enlarged 

 so as to cover most of the thorax and much of the abdomen, and 

 while in our species it is often extended into rather regularly formed 

 processes, yet in many tropical species these processes assume the 

 most irregular and grotesque shapes. In the subfamily Centrotinse, 

 however, the pronotum is not thus enlarged, but is so small that the 

 greater part of the scutellum is left exposed. 



As in all insects, the body is divided into three regions. The head 

 is quite characteristically homopterous, fitting against the coxae of 

 the prothoracic legs, between which lies the beak. At its lateral 

 extremities are the well-developed compound eyes, while the simple 

 eyes or ocelli are found on the i ertex, the paired sclerite forming 

 the greater part of the cephalic aspect of, the head. The ocelli are 

 always paired and in a line with each other and the compound eyes, 

 though their distance from each other and from the compound eyes 

 varies. 



The setaceous antennce are found under the margin of the vertex 

 on either side of the clypeus. The first three segments are large, but 

 the rest of the organ is composed of a large number of small 

 segments which decrease in size toward the apex. 



The vertex is a paired sclerite lying on either side of the base of 

 the Y-shaped epicranial suture. The presence of this suture would 

 indicate a mlore primitive position for this family than for the 

 Cicadellidae, where no signs of it are present. 



Between the arms of the epicranial suture and forming the apex 

 of the head is the clypeus. This sclerite is often characteristic in 

 the length of its apex and in its relation to the lateral margins of 

 the vertex. At its apex it is turned backward, forming a rounded 

 lobe, caudad of which are the genoi. The latter sclerites are seen 

 to form the lateral portions of the head, extending between the eyes 

 and the clypeus, and bearing the antennae. The postgence occupy 

 most of the caudal aspect of the head, forming, with the dorsal 

 occipital sclerites or occiput, most of the boundary of the occipital 

 foramen. The lorce are found on either side of the clypeus and 

 labrum as two more or less distinct sclerites with rounded lateral 

 margins. 



The beak or labium consists of three segments, as in other 

 Homoptera, and contains in a groo^'e the mandibular and maxillary 



