ROLAND HAYWARD. 17 



2. Anterior tibire with tlie apical spur simple 3. 



Anterior tibite with tlie apical spur trifid ; prothorax not wider in front of base : 



hind tibiiB pubescent on the inner side in the males... .v. Triseiia Lee. 



3. Prothorax distinctly wider in front of base 4. 



Prothorax not or scarcely perceptibly wider in front of base 5. 



4. Posterior tibiie not distinctly pubescent on the inner side in the males. 



iii. lieiocnenii!^ Zimm. 

 Posterior tibia; distinctly jnibeseent on the inner side in the males. 



iv. ISradytu»$ Zimm. 



5. Posterior tibite distinctly pubescent on the inner side in tiie males. 



vi. Ainara s. s. 

 Posterior tibije not distinctly pubescent on the inner side in the males. 



vii. Celia Zimm. 



Subgenus C'YRTOXOTl'S Steph. 



Prothorax distinctly wider iu front of ba.?e. Prosternuui not 

 margined at tip. Anterior tibiie with the apical spur simple. 

 Males with the middle tihiw dentate or bisiiiuate on the inner side. 

 Posterior tibioe not pubescent on the inner side in the males. 



The present subgenus includes our largest and most elongate spe- 

 cies. Morphologically it is separable from Leironotns only by the 

 structure of the middle tibiae of the males, while for its separation 

 from the other subgenera represented in our fauna an additional 

 character is afforded by the absence of a margin at the tip of the 

 presternum. The species composing it cannot, however, be confused 

 with any of the others, and, in fact, it forms one of the extremes of 

 the genus, some of its members bearing a much greater superficial 

 resemblance to Ptero^iichus than to the other subgenera. 



Some differences occur among the species in the dentation of the 

 middle tibite of the males. In all those occurring in North Ameiica, 

 except .1. hamatopa Dej. (simiiis Kirby), they are bidentate on the 

 inner side, w'lMe in the latter they are feebly bisinuate. The species 

 differ to so iie extent in the relative positions and prominence of the 

 teeth. ^1 one European species, ^4. auliea Panz., the middle tibia' 

 are tri entate. 



Ii addition to the difference in the structure of the middle tibia', 

 th« sexes are readily distinguishable by the dilation of the anterior 

 ta,rsi of the males and the difference in the number of anal sette, of 

 which there are two each side in the femtiles, one in the males. 



Nearly all the species of this subgenus are northern in their dis- 

 tribution, being represented in both the pahearctic and nearctic 

 regions. Several species have been described from North America 



TRANS. AM. ENT. SOC. XXXIV. (3) FEBRU A K Y. 1908. 



