Biology of the Membracidae of the Cayuga Lake Basin 335 



ment of teeth on the internal surface of the distal half (Plate xxxv, 16-19). 

 When teeth are present the distal end is expanded into a fiat plate, or disk. 

 In the simplest form the teeth are arranged around the edge of this disk 

 (Plate xxxv, 16) and the disk is often hollowed out in the center. The 

 commoner type, however, is the arrangement of the teeth over the surface 

 of the disk (Plate xxxv, 17), with those on the margin slightly larger 

 than the others. The disk is often elevated to a considerable distance 

 above the body of the trochanter, and its surface between the spines is 

 usually pebbled or thrown up into slight nodules. From a strictly lateral 

 view the edge of the trochanter appears merely dentate (Plate xxxv, 18), 

 and the opposite edges of the same disk are not uniform in number or 

 position of the teeth. In some species the teeth are very small, and 

 cone-shaped (Plate xxxv, 19), and in almost all cases they are jet-black 

 in color. 



An interesting feature in connection with the presence of the teeth 

 is the shifting of the attachment of the femur. Ordinarily the femur 

 is attached to the lateral end of the trochanter and extends more or less 

 laterally from the body. When the teeth are present, the plate, or disk, 

 that bears them is developed from the region at which the femur ordinarily 

 articulates. This forces the base of the femur around to the mesal rather 

 than the lateral angle, and the femur is thus forced to point farther inward 

 or else develop a curve in its proximal end. The faces of the toothed 

 disks of the two trochanters oppose each other when the legs are in the 

 normal position, and if the legs are brought close together the teeth meet 

 and interlock. 



No explanation has ever been offered as to the function of these teeth, 

 and their utility is questionable. They occur on both sexes and are 

 very constant. The nymphs show no suggestion of the structures in 

 the specimens that have been examined, but the material seen has been 

 extremely limited since most of the species that show the modification 

 are African and Asiatic and the immature forms are hard to obtain. So 

 far as the biology of these species is known, their life histories differ in no 

 respect from those of other forms that lack such structures. 



Another character that is apparently closely related to the toothed 

 condition is found in the hairs, or bristles, which often occur on the internal 

 face of the trochanter in many species. The fact that these bristles 

 are borne on the same area which gives rise to the teeth in the armed 



