336 W. D. FUNKHOUSER 



forms, and that the genera in which the bristles are found are closely 

 related to those that bear teeth, would suggest that the two forms of 

 modification may be the response to similar orthogenetic tendencies. 



The spined trochanters were first used in systematic work by vStal 

 (1866:89), as a character for the separation of his genera Tricentrus 

 and Sipylus. They have since been used as the primary character for the 

 genus Centrotoscelus (Funkhouser, 1914 a: 73). There can be little ques- 

 tion as to their importance in characterizing these three genera. Distant 

 (1908 a: 53), while admitting the value of the "armed trochanters" on 

 which- Stal so largely relied, raises an objection to their use as taxonomic 

 characters on the ground that they are difficult to distinguish. This 

 is hardly a valid criticism because of the fact that only the posterior pair 

 need be observed and these are plainly visible from a caudal view. More- 

 over it is merely the presence or the absence of the spines, not their 

 anatomical minutiae, which is required for diagnosis. 



The femora show the least variation of any of the leg segments in the 

 Membracidae. In shape the femur is usually club-like and often much 

 curved. The proximal end is swollen, and the segment gradually narrows 

 toward the distal end. The distal end is in some cases suddenly expanded 

 to form a knob, or head, and before this is a slight constriction, or 

 neck. The entire segment is subcylindrical, seldom flattened, and never 

 angular. It is the largest and strongest segment of the leg and doubtless 

 furnishes the chief power in jumping. The distal end is hollowed out 

 to receive the end of the tibia, and usually projects slightly on either 

 side into a plate to direct and strengthen the knee joint. The femur 

 is much inclined to pubescence, but in this respect it follows the general 

 tendency of the leg as a whole and does not differ from the other segments. 

 It seldom possesses a color pattern, even in gaudily decorated species. 



The knee joint, or joint between the femur and the tibia, offers an 

 excellent illustration of adaptation of structure to habit and is mechanically 

 interesting. The femur above is hollowed out on the dorsal margin 

 of the joint to form a fossa for the reception of the head of the tibia. 

 Laterad of this fossa occur smaller indentations to receive the lateral 

 teeth with which the head of the tibia is ,usually equipped. A'entro- 

 laterad of these indentations the lateral margins of the femoral lieati are 

 expanded to form projecting plates which hold the proximal end of the 

 tibia in place. The general structure is shown diagranmiatically in 



