6 BULLETIN 14 5, UNITED STATES NATIONAL MUSEUM 



depth, and care must be taken in making use of this character. The 

 prosternal process has the sides parallel, or expanded behind the 

 coxal cavities, and the apex is subject to great modifications. In 

 many of the species the tip enters the metasternum by a triangular 

 notch, while in others the tip is abruptly bent upward and is con- 

 cealed in the metasternum. When the tip is closely applied to the 

 metasternum, the part of the tip not concealed is triangular, rounded, 

 truncate or dilated. For convenience the visible free portion has been 

 assumed to be the tip, and is so spoken of in the descriptions. Sexual 

 dimorphism is here also well marked ; in some species the prosternal 

 process in the male is covered with fine, long, erect pubescence, where- 

 as in the female the surface is nearly glabrous. 



Abdomen. — The abdomen is more or less convex, and along the 

 sides is a distinct ridge, which is sometimes interrupted on the first 

 and second segments. Although this ridge is variable within cer- 

 tain limits, it is, not sufficiently so to use in the grouping of species. 

 This ridge divides the ventral segments from the vertical portions 

 of the segments which are sometimes more densely clothed with 

 pubescence than the ventral parts, and are frequently more or less 

 depressed and ornamented with pubescent spots. The suture be- 

 tween the first and second segments is usually entirely obliterated, 

 but rarely it is more or less indicated at the sides. The last segment 

 is either usually rounded or rarely truncate at the apex in our 

 species. The males of some species have a longitudinal vitta of 

 long, white hairs on the first and second segments, and the surface 

 is longitudinally depressed. 



Pygidium. — In nearly all of the species the surface is provided 

 with a median smooth or elevated line, in many species forming a 

 distinct ridge, and in some of the species the ridge projecting pos- 

 teriorly, and forming a spine which is truncate or emarginate at 

 the apex. The absence or presence of this projecting carina is one 

 of the most constant characters, and only varying in length. In 

 [nih-hellus the pygidium is acutely produced at the apex, with the 

 carina strongly elevated but not projecting beyond the apex. 



Legs. — The length of the posterior tarsi in comparison with the 

 tibiae is somewhat variable, but it is usually longer in the males 

 than in the females. In a large number of the species sexual dif- 

 ferences have been observed in the tibiae, consisting of a short tooth 

 or mucro on the inner margin at the apical angle of the anterior and 

 middle tibiae, sometimes on all of the tibiae of the males of some 

 species, but the tibiae of the females are usually not armed with a 

 distinct tooth at apex. A useful character is found in the form of 

 the tarsal claws ; these are either simply cleft, or cleft in such a man- 

 ner that the inner portions are turned inward, and the apices nearly 



