240 AMERICAN NEUROPTERA 



formed by a cloud in each cell, two clouds on anal margin near base, a black dot 

 at base of the pterostigma, basal veins white, around pterostigma white, vein 

 closing cell and base of the radial fork also white, otherwise the veins are black ; 

 hind wings unmarked, veins black ; cell four sided, as wide at apex as at base. 

 Length 7 mm. 



Districo Federal, Mexico (Barrett). 



PERLIDAE. 



It has long been recognized that the Perlidae could be divided into 

 two groups by the presence or absence of caudal setae. This, I con- 

 sider, a character of importance, yet hardly sufficient for subfamily 

 distinction. As of equal value, I would rank the position of the 

 anterior coxae. In an attempt to use the ventral structure for the 

 discrimination of genera, I discovered that the genus Pteronarcys 

 differs remarkably from all our other Perlidae in that the anterior 

 coxae are approximate and directed downward, while in the other 

 forms these coxae are well separated and directed outward. This 

 character, in connection with the other peculiarities of the genus, 

 warrant the erection of a tribe for it. The genus Capnia has long 

 been recognized as a very distinct one. The most important char 

 acter which distinguishes it (and allied genera) from Perla has not, 

 I think, ever been mentioned ; it is in the fact that the radial sector 

 is not furcate beyond the anastomosis. Despite the fact that in 

 many respects the venation of the Perlidae is often variable, there 

 are some points which appear fairly constant. The forking of the 

 radial sector, and a point in regard to Perla (as restricted) hold 

 true for all the specimens examined. These groups of Perlidae may 

 be considered as tribes. They can be separated in tabular form as 

 below : 



1. Caudal setfe absent Nemourini. 



Caudal seta? present 2. 



2. Eadial sector not furcate beyond anastomosis, veins rather heavy, small 



black species Capnini. 



Radial sector forked beyond anastomosis 3. 



3. Anterior coxre directed downward and approximate; venation of wings often 



irregular Pteronarcini. 



Anterior coxee directed outward and well separated ; venation more regular, 

 with fewer cross-veins Perlini. 



Our Pteronarcini include two genera, Pteronarcys and a new 

 genus, Pteronareella, for the two small species of Pteronarcys (hud in 

 and regularis) from the West. The latter genus is related to Dic- 

 tyopterx of the Perlini. 



