NATHAN BANKS. 241 



1. Iu the fore wing the space between basal part of radial sector and median 



vein is free Pteronareella. 



This space shows complete or incomplete cross- veins and cells which indicate 

 two rows Pfceronarcys. 



The Perlini is the most extensive tribe of the family, both in 

 genera and species. At present I separate in our fauna eight genera. 

 Several others will doubtless be erected as our knowledge of these 

 forms progresses. 



1. Apical space of fore wings with several transverse veinlets 2. 



Apical space of fore wings free or rarely with a few veinlets 3. 



2. Space hetween radius and radial sector with transversals.. Dictyopleryx. 

 Space between radius and radial sector free Acroneuria. 



3. No folded anal space to hind wings, small pale species Isopteryx. 



Anal space present 4. 



4. But two ocelli Pseudoperla. 



Three ocelli 5. 



5. Radial sector with a fork at or even before the anastomosis, normally con- 



nected in some way with the cross-vein closing the cell ; larger species, 



not greenish Perla . 



Radial sector with the first fork plainly beyond the anastomosis, not connec- 

 ted with the cross-vein closing the cell ... .6. 



6. Radial sector four forked ; never greenish species, a pale median stripe on 



prothorax Iwogeuus. 



Radial sector less than four forked, rarely more than two; smaller species. -7. 



7. Radial sector only once forked, if two, then greenish species, beyond end of 



subcosta usually but one transversal Cliloroperla. 



Radial sector usually at least two forked, if but once, then two transversals 

 beyond end of subcosta in costal area and not greenish species. 



Perlinella. 



The Capnini embraces three genera in our fauna. In Europe 

 there is another genus — Gapnopsis — which lacks the anal region to 

 hind wings (present in all our forms). The South American Grip- 

 hopieryx will probably fall in this tribe. 



1. Apical submarginal space with transverse veinlets- C'apuui'a. 



Apical submarginal space without transverse veinlets 2. 



2. Space beyond discal cell as long as discal cell Arsapnia. 



Space beyond discal cell shorter than discal cell Capiiia. 



Our Nemourini are grouped in three well-defined genera. This 

 tribe shows much affinity to the Capnini, but lacks the distinctive 

 character of the venation in many forms. The genitalia are often 

 very complex. 



1. Second joint of tarsus about as long as first Ta?niopteryx. 



Second joint of tarsus much shorter than the first 2. 



TRANS. AM. ENT. SOC. XXVI. (31) MAY, 1900. 



