346 W. D. FUNKHOUSER 



The positions of the thoracic spiracles, however, show that this one is 

 a part of the first abdominal ring, and a section of the early nj^mphal 

 stages leaves little doubt as to the correctness of this interpretation. 

 The spiracle of the second segment, likewise, is usually found at the very 

 edge of the sclerite if not actually in the membrane (Plate xxxvii, 1). 

 The sterna are uniform in the anterior region of the abdomen (second 

 to seventh segment, inclusive), but are modified in the posterior region 

 in the two sexes. Each sternum is typically a long curved plate forming 

 the ventral floor of the segment and connecting the pleura of each side. 

 Usually it is smooth and unsculptured. The abdomen is much thicker 

 at the anterior than at the posterior end, and for that reason the anterior 

 sterna are the longest and widest (Plate xxxvii, 3). 



The individual sclerites vary in certain respects in different genera, 

 but on the whole they show no difference important enough to warrant 

 special discussion. The relation of the various sclerites to one another 

 is seen in Plate xxxvii, 2, in which the entire abdomen, cut along the 

 median dorsal line, is shown as spread out flat. This species {Enchenopa 

 binotata) of the subfamily Membracinae shows the more extreme type 

 of variation. It will be noted that the first two sterna are rather peculiar 

 in shape, the seventh is subdivided, and the eighth is represented only 

 by two small triangvilar pieces. Aside from these not unusual peculiarities, 

 the abdomen as figured may represent the usual structure in the female. 



From an external view of a complete insect very little of the abdomen 

 is visible. The projecting posterior process of the pronotum hides the 

 dorsal surface, while the two pairs of wings fold tightly against the lateral 

 regions and conceal these areas. For these reasons the dorsal and lateral 

 parts of the abdomen are not suited for taxonomic study. It is doubtful, 

 however, whether these areas would offer characters of value even if they 

 were plainly visible. The color of the abdomen is usually uniform and 

 agrees with the general color of the remainder of the body. The under- 

 surface is generally darker than the upper, and the segments are in some 

 cases bordered with a lighter shade than that of the ground color. The 

 anterior end of the abdomen is inclined to be of a lighter hue than the 

 posterior, and all the segments are likely to vary in this respect within 

 a species. The entire abdomen, and particularly the ventral surface, 

 is much given to pubescence; this is very noticeable in certain forms along 

 the pleural sclerites. Occasionally the white tomentose patches are found 



