252 THOMAS SAY FOUNDATION 



Family CAPXIIDAE. 



Small blackish stoneflies, mostly less than 12 mm. 

 in length. Radius and media of forewing fused for a 

 considerable distance at the base and separating from 

 each other at a rather wide angle ; cerci composed of a 

 number of segments; middle segment of tarsus very 

 short. 



Head as wide or wider than prothorax ; lateral tubercles 

 and frontal ridge indistinct ; surface almost uniformly 

 dark brown or blackish ; three small ocelli, the hind ocelli 

 closer to the eyes than to each other. Antennae long, 

 dark brown. 



Prothorax quadrangular or wider than long; angles 

 mostly rounded ; surface not very rugose ; mostly con- 

 colorous. Legs brown or blackish, first and second tarsal 

 segments subequal, second segment very short. Wings 

 present in most forms, though often abbreviated ; radius 

 and media of forewing fused at base ; one median and 

 one cubital crossvein in forewing and these usually op- 

 posite each other; hind wing with a large anal field. 



Abdomen brown, cerci composed of few to many seg- 

 ments. 



Male. Supra-anal process modified into a recurved 

 probe; subanal lobes small, triangular; ninth abdominal 

 sternite only slightly produced and evenly rounded, with- 

 out a ventral appendage. 



Female. Eighth abdominal sternite not produced into 

 a distinct subgenital plate. 



Key to the Genera of Capniidae. 



1. Forewing with crossveins between Rl and R2 



Capnura 



Forewing without crossveins between Rl and R2 2 



2. Subcosta ends much before the cord ; anal field of 



hind large and nearly as long as the entire 

 wing; usually no crossvein in the space beyond 

 the tip of subcosta ; venation quite irregular ; 



mostly Eastern species C a pud la 



Subcosta reaches to or nearly to the cord; anal 

 field of hind wing not more than half the length 

 of the wing; usually a crossvein in the space 

 beyond the tip of subcosta; mostly Western 

 species Capnia 



