22 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.52. 



temples are narrow. The ocellar cicatrices are circular or nearly so 

 and are sunk in pits, the anterior one having a conspicuous elevation 

 round about it. 



The outer border of the mandible is entire, the inner is provided 

 with one or two teeth and the apex is simple. The labrum is longer 

 than broad at the base, not strongly arched, roundly truncate at the 

 apex, but not emarginate. The maxillae are well developed, rela- 

 tively as long as in the genus Stictia, half conical in shape and forming 

 a tube enclosing the tongue which is strongly divided at the apex. 

 The maxillary palpi are composed of six segments and the labial of 

 four. The clypeus is much broader than long, and very slightly 

 arched. There is no proximal median carina and no distal flattened 

 median area. The distal border is curved. The antennae are inserted 

 on the frons quite close to the clypeus and their insertions divide the 

 distance between the compound eyes into three equal parts. In the 

 male the antenna consists of thirteen segments, in the female of 

 twelve. The flagellum of the male seldom shows conspicuous sec- 

 ondary sexual modifications, and consequently is of little use in the 

 separation of species. 



The dorsum of the thorax is relatively flat, but the posterior border 

 of the prothorax is much below the level of the scutum, and the 

 tubercles do not reach the tegulae. The suture between the sternum 

 and the episternum of the meso thorax is obliterated. The median 

 segment is short, its lateral angles are rounded, and its posterior sur- 

 face nearly vertical and flat. The dorsal middle-field is clearly 

 defined and is broadly continued on the posterior surface. 



The wings are usually clear, rarely somewhat infumated. The 

 radial cell at its distal end is narrowed and rounded and lies on the 

 costal border of the wing. The first cubital cell in length exceeds the 

 second and third combined. The first cubital cross vein is usually 

 straight, in some species slightly bent near its junction with the 

 cubitus but never so strongly as in the case of Stictia or Bembix. 

 In many species the second cubital cell is about as wide on the radial 

 as it is on the cubitus, but in others this cell is decidedly narrowed on 

 the radial. It receives both discoidal cross veins. The third cubital 

 cross vein is strongly bent outward, but its form and consequently 

 the form of the third cubital cell vary somewhat in the different 

 species. This cell extends as far toward the distal end of the wing 

 as the distal end of the radial cell, and the angle formed by the radial 

 and third cubital cross veins and opening outward is acute. The first 

 submedian cell is longer than the second, which increases in breadth 

 toward its distal end. The basal vein arises a short distance proxi- 

 mal to the distal end of the submedian cell. 



On the hind wing the retinaculum, consisting of an unbroken row 

 of hooHets, begins a short distance proximal to the origin of the 



