286 



Illinois Natural History Survey Bulletin 



Vol. 23, Art. ] 



KEY TO NEARGTIC SPECIES 



Males 



1. Tenthjtergite forming a pair of short, 



broad, sclerotized plates, fig. 952. . . 



rufa (Hagen) 



Tenth tergite forming a pair of long, 

 bladelike plates well separated on 

 the meson, fig. 954 2 



2. Apical processes of tenth tergite long 



and sinuate, basal hook arcuate but 



not curled, fig. 953 amera (Ross) 



Apical processes of tenth tergite wide 

 and only slightly sinuate, basal hook 

 curled, fig. 954 3 



3. .Apical segment of clasper with a very 



long, stout mesal tooth, fig. 954. . . 

 labida n. sp. 



Apical segment of clasper with several 

 short teeth but without a long mesal 

 one, fig. 955 4 



4. Ninth segment with a long, slender 

 style running beneath cerci; apical 

 segment of clasper short, fig. 955. . . 



frontalis Banks 



Ninth segment without any process of 

 this kind; apical segment of clasper 

 long, armed with many teeth, fig. 

 956 indecisa (Walker) 



Psilotreta rufa (Hagen) 



This species has been placed in various 

 genera, but the genitalia clearly indicate its 

 affinity with other members of the genus 

 Psilotreta. The species connexa, described 



Figs. 952-956.— Psilotreta, male genitalia. J, lateral aspect; B, clasper, caudal aspect; 

 C, tenth tergite. 



