118 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.52. 



but when folded are concealed behind the labrum. The maxillary 

 palpus is composed of three segments, the labial of one. The labrum 

 at the apex is conical and truncate, but is flat at the base where it 

 joins the curved distal border of the clypeus. On some specimens the 

 labrum shows a slight median longitudinal depression. The clypeus 

 is very strongly arched, in fact almost angular, and the distal part of 

 the median prominence is devoid of pubescence, smooth, and shining. 

 The distal margin is strongly curved, almost semicircular. The an- 

 tennae, which are inserted on the frons, apparently on the suture 

 joining the frons and clypeus, are composed of 13 segments in the 

 male and of 12 in the female. The scape is heavy and exceeds in 

 length any segment of the flagellum. The first segment of the flagel- 

 lum (pedicel) is short, about as long as thick, and the second exceeds 

 in length any of the following segments. Some of the flagellar seg- 

 ments on the male bear secondary sexual modifications. 



The thorax is quite similar to that of Bembix, but the abdomen is 

 more slender. The ultimate tergite of the female is arched and 

 strongly punctate except on the midline, where there is evidence of 

 a slight longitudinal carina. Laterally the tergite is beset with short 

 spines and it terminates in a median notch, the sides of which may 

 be prolonged into evident spines. The second sternite of the male 

 bears a median process that by its form and development affords 

 specific characters. 



The male genitalia consist of a basal piece (cardo), paired stipites, 

 paired sagittae, and median spatha. The base of the stipes is heavy, 

 but the distal part is slender and hirsute and varies in form with the 

 different species. The spatha is short and heavy and distally is cleft 

 below. Near the distal end on either side is a conspicuous rounded 

 enlargement, and the apex is in the form of a tube split below. The 

 sagitta is composed of two parts; the inferior one is short, sparingly 

 hirsute, and more or less concealed; the superior part is strongly 

 chitinized, curved, compressed, dilated distally, and truncate 

 apically. 



The legs are moderately long and slender.. On the female the first 

 four segments of the anterior tarsus are flattened and the posterior 

 distal angle is greatly prolonged. These four segments are provided 

 with long strong pines that form the tarsal comb used in burrowing. 

 On the male the comb is present but not so well developed. The 

 wings may be infumated or entirely hyaline. On the anterior wing 

 the radial cell is pointed at either end and the distal end does not lie 

 on the costal border. The first cubital cell is as long as the second 

 and third combined. The second cubital cell is narrower on the 

 radial vein than it is on the cubitus, and it receives both discoidal 

 cross veins. The first cubital cross vein is straight, and the third, 

 which curves toward the distal extremity of the wing, forms with the 



