1919] Hine: Genus Erax 117 



Erax aridus Williston. 



The female type of aridus is in the National Museum. There does 

 not appear to be any male specimens at hand. The species is peculiar 

 in being very hairy and bristly and Williston described it as belonging 

 near latrun cuius, but it surely is very distinct from that species. True 

 there is a row of rather long black hairs in the middle of the anterior 

 part of the dorsum of the mesothorax, but the thorax is not compressed 

 and it is almost sure that when the male of aridus is finally located 

 it will not have a dilated costa which is always present in the carinatus 

 group. Palpi with black hair, vestiture of remainder of head pale, 

 mesothoracic dorsum with black hair, scutellum with light hair, bristles 

 near the wing bases pale, pleurae pale haired, legs with abundance of 

 long pale hairs, and mostly pale bristles, legs black, base of each tibia 

 with just a suggestion of reddish, wings hyaline, furcation of the third 

 vein nearly opposite the base of the second posterior cell, stump dis- 

 tinctly longer than the basal section, abdomen black, gray pollinose, 

 more plainly so laterally and on the narrow posterior border of each 

 segment. Oviduct black, short, only a little longer than the last two 

 abdominal segments. 



The short oviduct readily separates aridus from what is 

 considered as the female of suhpilosus a nearly related species. 

 For a time the possibility of the type of suhpilosus being the 

 male of aridus was considered but there seems to be good reason 

 for separating them as distinct. Length about 25 millimeters. 



Williston's type was taken by the Death Valley Expedition 

 in April, 1891. 



Erax prattii n. sp. 



Male. Total length 16 millimeters. Mystax and beard white, 

 palpi with black bristles, front mostly with pale hairs, several bristles 

 near the ocelli, some black and the others yellow, occipito-orbital bristles 

 pale yellowish. Bristles and hairs of the mesothoracic dorsum black, 

 pleurae white hairy; legs abundantly long white hairy and with black 

 and pale bristles, femora black, tibiae and tarsi mostly pale brownish; 

 wings hyaline, costa not at all dilated, branching of the third vein 

 almost exactly opposite the base of the second posterior cell, stump 

 scarcely as long as the basal section. Abdominal segments one to five 

 inclusive black, each with a narrow gray border of uniform width, 

 segments six and seven silvery. Hypopygium from dorsal view grad- 

 ually widened from base to apex, where it is nearly truncate and dis- 

 tinctly wider than in most other species. See Figure 13. 



Male type from Laredo, Texas, November 25, 1905. Col- 

 lected by F. C. Pratt, from whom the specimen was procured. 

 Collection of the author. 



The size and the width of hypopygium make it easy to deter- 

 mine this species. 



