NO. 2173. A REVISION OF THE BEMBICINE WASPS— PARKER. 57 



occiput is quite narrow and tlie posterior surface of the head vertical 

 and flat. The temples are narrow. Tlie mandibles on their anterior 

 border are entire; on their posterior border they are provided with 

 two teeth and the apex ends in a point. The maxillae are moderately 

 long, and when folded at rest they are concealed beneath the labrum. 

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

 four. The labrum is about as long as broad at the base, somewhat 

 arched from side to side and broadly rounded at the apex, not 

 emarginate. The clypeus is broad and arched and its lower border 

 is slightly curved. 



Tlie antennae are inserted on the frons on either side of the median 

 carma a short distance above the base of the clypeus. They consist 

 of 12 segments in the female and of 13 in the male. In the case of 

 the males of some species some of the flagellar segments show sec- 

 ondary sexual modifications that are of use as characters in the dis- 

 tinguishing of species. Tlie first flagellar segment (pedicel) is about 

 as thick as long and the second exceeds any of the following ones in 

 length. 



The dorsum of the thorax is comparatively flat and the collar is 

 placed much below the level of the scutum. The tubercles do not 

 reach the tegulae. The suture between the sternum and episternum 

 of the mesothorax is obliterated. The surface of the metapleura is 

 ahnost at right angles to the long axis of the body and as a result its 

 junction with the side of the median segment forms a depression into 

 which the femora of the middle leg is drawn when at rest. The 

 median segment shows a clearly defined dorsal middlefield which 

 extends down upon the posterior surface of the segment. In a man- 

 ner that is characteristic of the species of this genus the lateral angles 

 of the median segment are extended, strongly compressed and wedge- 

 hke, and consequently the posterior surface of the segment from side 

 to side is conspicuously curved or concave. The tergites are arched, 

 the sternites flat, and in general the abdomen appears relatively longer 

 and more slender than in Bemhix. In the case of the female of some 

 species the ultimate tergite bears a more or less well defined pygidial 

 area set off by lateral ridges. The eighth sternite of the male, con- 

 cealed beneath the seventh, ends in three spines instead of one as in 

 Bemhix. On none of the species so far recorded from North America 

 north of Mexico do we find processes on the sternites of the males. 

 The male genital apparatus consists of a short basal piece that sub- 

 tends the long, strongly hirsute, weakly chitinized, lateral stipites, 

 variable m form among the species, the median cleft spatha, which, 

 seen from above, ends m a prominent rectangular dilation, and below 

 the spatha the sagittae. Each sagitta is composed of two parts; the 

 mferior part is straight, relatively slender, weakly chitinized and 

 hhsute; the superior part is curved somewhat, strongly chitinized 



