1919] Hine: Genus Erax 139 



appears to be the western representative. Over much of its 

 range the species is very differently colored from riifibarbis, 

 but the two approach each other in some localities. An 

 occasional specimen has three submarginal cells either in one 

 or both wings. The furcation of the third vein averages 

 slightly further forward in bicaudatus than in rufibarbis, but 

 this is variable within limits in both species. Specimens have 

 been sent in under no less than half a dozen different specific 

 names. 



The stramineus Group. 



One of the largest groups of the genus Erax is characterized by 

 having the furcation of the third \^ein distinctly anterior to the base of 

 the second posterior cell. In most all the species the mesothorax has 

 many bristles posteriorly and the scutellum has many bristles on its 

 margin and often numerous long hairs on its disc. Practically all the 

 species are western or southern in distribution. 



1. Furcation of the third vein at or before the middle of the distance between 



the base of the second posterior cell and the small cross vein 2 



Furcation of the third vein distinctly beyond the middle of the distance 

 between the ba;se of the second posterior cell and the small cross- vein. ... 18 



2. Male abdomen without long hair parted at riiiddle and directed outward 



on one or more seginents 3 



Male abdomen with long hair parted at the middle and directed outward 

 on one or more segments 5 



3. Hypopygium from side view plainly divided at tip, oviduct conical, 



interruptus Macquart 

 Hypopygium from side view not divided 4 



4. Hypopygium from side view narrowest at apex, tibiae basally bright reddish 



yellow texanus Banks, n. sp. 



Hypopygium from side view not narrowed at apex, tibiae basally dark reddish 

 brown califomicus ShaefTer 



5. Mystax yellow 6 



Mj^stax not yellow 11 



6. Tibiae at least largely red 7 



Legs black 9 



7. Male third abdominal segment only with long white hair parted at the 



middle and directed outward aurivestitus n. sp. 



Male abdomen with at least four segments with long white hair parted at 

 the middle and directed outward " 8 



8. Abdomen white haired to base. Hypopygium with a rather conspicuous 



tuft of hair inferiorly at apex canus Hine 



Abdomen, especially the male, conspicuously darker on first and second 

 segments than on the following ones, no tuft of hairs at apex of Hypopygium, 



dubius Williston 



9. Body conspicuously dark colored, male with abdominal segments four, five 



and six only, white haired splendens Williston 



Body largely yellowish gray poUinose, male with abdominal segments three 

 to seven inclusive white haired 10 



10. Usually not to exceed 18 millimeters in total length stramineus Willis. 



Specimens 20 millimeters or over in length rapax Osten Sacken 



11. Mystax composed of black and white bristles and hairs intermixed 12 



Mystax wholly pale 13 



