MORGAN HEBARD 103 



PAPER TWO 



The Group Hyalopteryges as Found in the United States 



AND Canada 



A single species of this group is found in the area under con- 

 sideration. This is Truxolis hrevicornis (Johannson), the only 

 species of the genus. The insect is a simple Hyalopteiygine 

 type, as shown by the general structure and particularly by the 

 strikingly fenestrate wings of the male. The highest speciali- 

 zation in the group occurs in the South American genus Hyalop- 

 terijx. There are no other North American genera of the group, 

 though Thyriptilon Bruneri and Orphula Stal," species of both 

 of which genera occur in Mexico, are aljerrant Orphulellae 

 showing convergence toward the Hyalopteryges in having the 

 male wings strikingly fenestrate. 



The genera of the Group Hj^alopteryges now recognized are: 

 Hyalopteryx Charpentier, Eutryxalis Bruner, Truxalis Fabricius 

 and Paratruxalis Rehii. In linear arrangement of the North 

 American genera, found north of JNIexico, we place Truxalis 

 after Mermiria and before Syrbula, which, of course, represent 

 other genera groups. 



The following characters are important in distinguishing this 

 genus and species. 



Head weakly ascending, its dorsal length shorter than that 

 of the pronotum. Vertex roundly produced, a little longer 

 than wide, showing a very weak medio-longitudinal carina; 

 lateral foveolae weakly indicated, small, triangular, facing 

 laterad; face rather strongly oblique. Pronotum with disk 

 flattened, having distinct, straight, weak medio-longitudinal 

 and lateral carinae; metazona nearly three-fourths as long as 

 prozona; lateral lobes vertical, distinctly, but not decidedly, 

 longer than deep. Tegmina and wings fully developed; the 

 former obliquely truncate distad; the latter, in the male sex, 

 with a fenestrate area as figui'cd. Caudal ftnnora with dorsal 

 genicular lobes alone feebh' produced, the internal very slightly 



^ Bruner's Sisantum is a syncnjin of Thyriptilon, as comparison of the 

 types of the two geiiotypic species convincingly shows. 



"The difficulties surrounding the proper application of this generic name 

 have been eradicated by Rehn, Trans. Am. Ent. Soc, xlii, p. 275, (1916) 

 and Idem, xlhi, p. 344, (1917). 



TRANS. AM. ENT. SOC, XLVIH. 



