1919] Hine: Genus Erax 115 



Several specimens from Colombia, South America, from the 

 Carnegie Museum of Pittsburgh. Other specimens from Mexico. 



Erax bimaculatus Bellardi. 



Total length 25 to 28 millimeters. Mystax and beard pale yellow, 

 the former with a few black bristles above; thorax brown pollinose 

 with the usual markings; wings yellowish, costa of male distinctly 

 dilated, femora black, remainder of legs yellowish red with black 

 bristles. Abdomen colored much as in quadrimaculatus in the male seg- 

 ments four and five entirely silvery, or at most with a very narrow mid- 

 dorsal stripe, segment seven silvery on front margin and on the sides, black 

 otherwise, female with abdominal segments two, three and four white 

 pollinose on the sides, fifth white with the exception of a mid-dorsal 

 stripe, sixth and seventh velvety black, oviduct shining black. 



The yellow mystax and beard readily separates this species 

 from quadrimaculatus. The two species are entirely distinct 

 although similarly colored. 



' Several specimens from Guadalajara, Mexico, collected by 

 McClendon, and from Cuernavace, Mexico, collected by D. L. 

 Crawford. 



The aridus Group. 



A few species from the more or less arid regions of western United 

 States are much like members of the stramineus group, but the branching 

 of the third vein is almost exactly opposite the base of the second 

 posterior cell. The following key may be used to separate the species. 



1 . Mystax straw yellow 2 



Mystax white 3 



2. Male abdominal segments six and seven, silvery harveyi n. sp. 



Male abdominal segments four, five, six and seven silvery. Four more or less 



black on the mid-dorsal line snowi n. sp. 



3. Hypopygium from dorsal view plainly widened towards apex where it is dis- 



tinctly wider than at base prattii n. sp. 



Hypopygium not or but very slightly wider at apex than at base 4 



4. Bristles of the body and legs nearly all white, male first and second abdominal 



segments black hairy subpilosus Schaeffer 



Male first and second abdominal segments white hairy aridus Williston 



Erax harveyi n. sp. 



Male. Total length 18 millimeters. Mystax, beard, ocellar and 

 occipito-orbital bristles pale straw 3'ellow, palpi black and yellow 

 haired, anterior part of dorsum of mesothorax black haired, remainder 

 of thorax with pale vestiture, scutellum with numerous pale yellow 

 marginal bristles; wings hyaline, furcation of the third vein exactly 

 opposite the base of the second posterior cell, stump about as long as 

 the basal section; legs faded reddish, mostly with pale vestiture, but 

 an occasional black bristle, femora quite distinctly darker than the 

 other parts. Abdomen pale haired all over, general color dark, thinly 



