104 Ajinals Entomological Society of America [Vol. XII, 



Banks, J. C. Bradley, Charles Schaeffer, R. H. Beamer, C. P. 

 Alexander, F. R. Cole and A. L. Lovett. Much material has 

 been procured also by purchase or exchange from others who 

 have expressed interest in the work. 



Having at my disposal an extensive collection of the species 

 of Erax from a wide range of territory in North America, a 

 careful attempt has been made to properly identify the species 

 concerned. Types have been studied in all cases where such 

 were available. In some instances descriptions had to be used 

 entirely and since some of these descriptions, of older authors 

 especially, are brief and indefinite it is not impossible that 

 oversights have occurred. The external male genitalia are used 

 much in designating species. The vestiture of these organs 

 obstructs one's view at times, but the dorsal part is less obscured 

 than the ventral, so the former has been outlined more care- 

 fully, and is the part to which students are referred as an aid to 

 specific determination. 



It has not been possible to reach a conclusion in regard to 

 the identity of some of the species so the following names are 

 not included in the descriptive part of the paper: 



Erax comatiis Bellardi was not identified in the material 

 studied. It belongs to the carinatus group and is described as 

 25 millimeters in length. 



Erax a per Walker very likely belongs to the carinatus group 

 also but it was not identified. It was described from Mexico 

 and may be one of the species mentioned in the paper but its 

 description is indefinite. 



I consider Erax pumilus Walker and Erax disjunctus Williston 

 the same as Eristiciis ?iigripes Bellardi. This species is consid- 

 ered in Trans. Am. Ent. Soc. XLIII, 297, under Eicherax 

 nigripes. The insect is not mentioned either by Osten Sacken 

 or Williston in their works on Central American Diptera. 



Erax pavidus Williston, from Mexico, appears to be well 

 characterized but it was not identified in the material studied. 



Erax lascivus Wiedemann, Asilus amarynceus Walker, 

 Asilus flavofasciatus Wiedemann, Asilus macularis Weidemann 

 and Asilus antiphon Walker, most likely are all species of Erax. 

 They have been reported from North America and most of them 

 from South America also. Records of their occurrences are 

 meager and they have not been identified in recent years. 



