Xlii INTRODUCTION. 



Terminology. 



The Exoskeleton of the Tettigidas accords pretty 

 closely with that of the general Homoptera, except 

 that certain adaptive parts appear in the abdominal 

 segments. 



The head, thorax, and abdomen are distinctly divided 

 from each other. 



The upper wings or elytra are sometimes so com- 

 pletely coriaceous that the name Hemiptera is not 

 very apposite to this group. 



The Head. Cap^it. Tete. Kopf. 



The variable form of the head is to be noted. It 

 occurs square, pointed, round, wedge-shaped, and even 

 cylindrical, as in the Continental Dorijdium. Most 

 commonly the ocelli — in number two, or more rarely 

 three — are placed on the vertex or crown ; the crown 

 may be raised into tubercular masses, as seen in 

 Cicadctta, or at other times the surface may be flat, or 

 five-sided as in Ledra. When viewed in profile, 

 the prone and half-horizontal aspect of the frons or 

 face is striking; and also the peculiar mode in which 

 the antennae spring from the under-side of the face. 

 The head is sometimes overshadowed and partially 

 concealed by the pronotum. 



The caput is divided into the vertex or crown 

 (scJieitel), the frons or face {stirue), the G\j])ei\s(kopfschild), 

 or the divided space below the frons, and below this 

 projects the rostrum or proboscis {schnahchchcide). The 

 lora consist of spaces bounded by the angles made by 

 the sides of the frons and the clypeus; the genae or 

 cheeks ; and the open spaces above and near to the 

 eyes, styled the tempera, complete the under parts of 

 the head. 



On the vertex we usually find the ocelli or stemmata ; 

 but in the FulgoridtB these are transferred to a space 



