6 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.52. 



tened, median area near the base, on either side of which there is a 

 slight, rounded prominence. 



The clypeus is arched, wider than long, its apical border straight 

 or slightly arcuate; it bears a slight median carina continuous with 

 the carina between the antennae. These are long and slender and 

 possess few characters of value in separating species, although in the 

 case of the male of some species several of the flagellar segments are 

 carinate on the posterior suface. The antennae are inserted on the 

 frons quite close to the basal margin of the clypeus and the distance 

 between the points of insertion is slightly less than the distance from 

 the point of insertion to the inner margin of the adjacent eye. They 

 consist of 13 segments in the male and of 12 in the female. 



The collar, or posterior border of the prothorax, is quite narrow 

 and is placed much below the level of the scutum. The tubercles do 

 not reach the tegulae above. The scutum, scutellum, and metanotum 

 are relatively flat. The epimeron of the mesothorax is well denned, 

 but the suture uniting the episternum and sternum of the mesothorax 

 is lacking. The metapleura joins the side of the median segment 

 almost at a right angle, thus forming a depression into which the 

 femur of the middle leg is drawn when at rest. 



The median segment is rather short and tapers toward the pos- 

 terior. Its lateral angles are not compressed but are rounded off. 

 As in related genera, the dorsal middle-field of the median segment is 

 large, plainly set off, and is extended down upon the nearly vertical 

 posterior surface of the segment. The tergites are arched, the ster- 

 nites almost flat. On no species is there found a pygidial area set off 

 by lateral lines on the ultimate tergite of the female. The second 

 sternite of the male bears near its posterior margin a median, pointed, 

 backwardly directed, tooth-like process that in most species is promi- 

 nently developed, but in one is quite rudimentary. The sixth ster- 

 nite is without a process of any kind in this genus and the seventh is 

 concealed beneath the sixth. The eighth sternite of the male ends 

 in three spines and a fourth is present upon the disk. The develop- 

 ment of the spines affords specific characters. The genitalia of the 

 male consists of a short basal piece, which bears the long lateral 

 genital stipites, a pair of median curved sagittae, above which on the 

 median line lies the spatha which ends in a pair of hooks. 



The front wing. The pterostigma is vestigial. The radial cell, 

 which is nearly as long as the first cubital cell, is narrowed toward its 

 apical end, which lies on the costal border. Of the three cubital cells 

 the first is long, exceeding the combined length of the second and 

 third. The second is shorter than the third, rectangular in form 

 though usually somewhat narrowed on the radial vein; it receives 

 both discoidal cross veins. The third cubital cross vein is strongly 

 bent toward the apical border of the wing but does not extend far- 



