204 DIPTEEA. 



disappearance in the male of the stump on the anterior branch of the third vein, although 

 it is fully developed in the female. In the figures of the males of E. parvulus, Bell., 

 and E. carinatus, Bell. (cf. Saggio &c. ii. t. 2. ff. 8 & 9), the stump is erroneously repre- 

 sented as being present. I have seen the typical specimens, in which it is wanting ; and, 

 moreover, the description in both cases says explicitly "cellula inappendiculata," 

 although the cell is incorrectly called " first posterior." 



9. Erax ? 



Hah. Mexico, Northern Sonora (Morrison). 



A single male, about 12 millim. long without the forceps. This specimen has 

 the silvery abdomen beset with rather long silvery hair, which, beginning on the 

 second segment, is parted in the middle and combed outwards ; there seem to be 

 some darker spots on the silvery ground of the second segment, but they are con- 

 cealed by the hair ; the venter beset with long white hair. The crest of erect black 

 hairs on the thorax is more dense here than in E. prolijicus, almost reaching the 

 scutellum ; on each side it has a fringe of short, delicate, white hairs closely applied to 

 it ; the tuft of scattered black and white hairs which, in E. prolificus, exists between 

 the thoracic suture and the scutellum is replaced here by the prolongation of the black 

 crest ; hairs on the scutellum snow-white (except the usual fringe of black bristles) ; the 

 hairs of the beard and mystax also of a purer white than in E. prolificus, those of 

 the mystax mixed with black, especially on the upper part. Wings like those of 

 E. prolificus, only a little purer hyaline ; the thickening of the costa is similar, that is, 

 only moderate, and less strong than in Erax No. 10. Prevailing ground-colour of the 

 legs dark metallic green ; tibiae deep red on the proximal half only ; coxae, femora, and 

 tibiae beset with white hairs. Forceps of the same structure as in E. prolificus, only 

 the upper part projects much less beyond the hairy brush on the underside. 



Two females from the same locality may perhaps be paired with the above-described 

 male. One, without the ovipositor, is 15-16 millim. long ; the other 11-12 millim. In 

 these specimens the black crest on the thorax does not reach so far back as in the male, 

 but is replaced beyond the suture by scattered black hairs, with a strong admixture of 

 white ones (as in E. prolificus). The abdomen is black above, with narrow grey margins 

 to the segments, the lateral margins more broadly grey ; with long white hair on the 

 upper surface of segments ]-3, and shorter white hair on the hind margins of the 

 following segments ; the ovipositor equal in length to five of the preceding segments. 

 Legs beset with long white hair ; femora dark metallic green ; tibise reddish, darker 

 towards the tip. The mystax with black hairs, mixed with white ones, some rufous 

 hairs also appearing among them. The coxae with tufts of rufous hair, which are, how- 

 ever, much less apparent in the smaller specimen. I doubt that these hairs are a 

 permanent character. These females are easily distinguished from the same sex of 



