FAM. MEMBRACID.E 3i 



these organs is present and the relative position in the segment is comparatively uniform throughout 

 the family. Each style arises from the lateral margin of the segment near its base and usually between 

 the lateral valves and the sternal plate. On dissection it is seen that the base extends into the abdomen 

 and originates in the seventh segment. The style projects almost directly caudad and sometimes 

 shghtly laterad. • In shape the basal part is comparatively straight and the distal end bends upward 

 in a gradual curve or sharply at an angle. The tip is the most inclined to variation, and may range 

 from a sharp, needle-like point to broadly angled plates or sharply toothed hooks. Study of the process 

 of copulation in the living insects proves the function of the styles to be that of clasping or inter- 

 locking organs, as their shape would indicate. The terminal hook or angle always turns upward and 

 in some cases forward. In a few species examined, the styles act in conjunction wilh the teeth of the 

 lateral plates in the mating process. As in the case of the oedagus, the structures of the styles offer 

 suggestive taxonomic characters and may be found useful in a number of genera. 



The sternal plate is apparently a modified abdominal sternum, but its tendency to subdivision 

 would suggest that it may be a fused or partly fused pair of appendages. The plate originates at the 

 base of the ninth segment and is attached to the eighth abdominal sternum. It piojects first caudad 

 and then dorsad and is the most posterior of the genital organs. It may extend only a short distance 

 upward, or it may extend so far in this direction as to hide the other genitalia when viewed from a 

 caudal aspect. It usually shows a division down the median line. This division may show only a 

 shght notch, or the separation may be so apparent as to show two distinct plates ; but in aimost every 

 case the two halves of the plate may be pulled apart after boihng in caustic potash, showing the real 

 structure of the sclerite. For systematic purposes the appearance of the plate in the complete insect, 

 rather than a theory as to its anatomical conditions, is of course of more practical importance. This 

 can usually be best ascertained from a strictly caudal view, and the characters most easily noted are 

 the comparative length of the plate, the shape of the upcurved part, and the amount of sphtting 

 at the tip. All these points show sufircient variation to aid in diagnosis and all are relatively constant. 

 The sternal plate is usually pubescent and often covered with stiff, bristle-hke hairs. It is freely 

 movable and in the ralaxed specimen may be pulled far downward without injury to itself or to the 

 remainder of the genitaha. It may often be examined by merely separating the wing tips, and for 

 that reason is the best adapted of all the genital parts for systematic work. 



On the whole the male genitaHa afford good taxonomic characters. The parts are simple and 

 easy to dissect. The relative position of the plates and the structure of the individual pieces show 

 sufficient variation throughout the family, and are constant enough within a genus, to furnish valuable 

 data at least to supplement the more evident characters of the exoskeleton. 



INTERNAL ANATOMY 



The internal anatomy of the membracid does not, on the whole, differ enough from that of other 

 Hemiptera to warrant special discussion. The digestive system, however, shows some pecuUarities. 

 Kershaw (igiS) found that in the species Tyicentrus albomaculatus the ahmentary canal showed a formation 

 ofthe mid-intestine very similar to that reported by Packard (1898) for the Psyllida, with accessory 

 organs consisting of four uriniferous tubules. The writer has found this same condition present in the 

 genus Gargara and in certain other forms of the Centrotina. 



By far the larger number of membracids, however, including all of the Smiliinte which have been 



