380 HYMENOPTEEA. 



radius is oblique ; the first recurrent nervure is received in the basal third of the 

 cellule; the third transverse nervure is completely obsolete, except a very obscure 

 stump at the top ; there is only one recurrent nervure ; the basal nervure is not 

 interstitial. 



The fact of this species (and the same may be said of others) having the stump of 

 the third transverse cubital nervure indicated at the top, shows that the number of 

 marginal cellules in this group cannot be used as a generic character, and must even be 

 used cautiously in splitting up the genus into sections ; for even in the same species 

 we find this nervure much more faintly traced in some specimens than in others. The 

 same remark applies to the absence of the second recurrent nervure, which shows an 

 equal tendency to become obsolete, it being fainter in some specimens than in others 

 of the same species. 



The following species (S. lacuna) has the abdomen shorter and broader than in any 

 of the other members of this section here described, it being, if anything, shorter than 

 the head and thorax united ; the petiole is more than half the length of the abdomen, 

 much narrowed at the base, and broadly dilated at the apex, the dilated part not being 

 much narrower than the thorax ; the depression on the sternum is deep and wide, 

 particularly towards the apex, in front of the coxae it is very deep, the base of the 

 depression being oblique, on the inner side it is separated from the central longitudinal 

 furrow by a sharp keel. 



136. Sphserophthalma lacuna. 



Long. 10 millim. tf . 



Hah. Mexico, Northern Sonora (Morrison). 



The head very slightly narrower than the mesothorax, deep black, shining, impunc- 

 tate, almost glabrous, the clypeus and mandibles ferruginous, the tips of the latter 

 black ; behind the eyes it is narrower, not half their length, and rounded. The ocelli 

 are prominent ; a furrow surrounds the anterior ocellus and from the centre of this 

 furrow a straight keel runs to the antennae. The antennae ferruginous, covered with a 

 pale microscopic down ; the basal joint stout, sparsely covered with longish white hair; 

 the third and fourth joints equal in length (the joints beyond the sixth broken off). The 

 thorax shining, almost impunctate, sparsely covered with White hair ; the parapsidal 

 furrows reaching to the scutellum, but not to the pronotum ; there is a transverse 

 furrow at the base of the scutellum, which is flat and very shining. The median segment 

 has a gradually rounded slope to the apex, smooth, shining, impunctate, or, at most, 

 faintly shagreened. The pleurae smooth, shining, sparsely covered with soft white hair. 

 The abdomen is shorter than the head and thorax united ; the basal third of the petiole 



