THE CANADIAN ENTOMOLOGIST. 223 



few names may require ex43lanation. Perlodes replaces Didyopteryx, as 

 the latter name is preoccupied in Lepidoptera ; Neoperla replaces 

 Pseudoperia, the latter having been used previously in the Orlhoptera. 

 Prof. Klapalek, who has seen the type of Tcoiiopteryx fasciata^ Burm., 

 places it in the genus Rhabdiopteryx. 



Pteronajxini. 

 I. In the fore wings the space between the basal part of radial sector 

 and median vein shows some complete or incomplete cross-veins ; 



larger species Pteronarcys. 



This space is free from cross-veins ; much smaller 



species Pteronarcella. 



Periifii. 

 I. Many cross-veins between apical branches of the radial sector, as well 



as between radius and radial sector Perlodes. 



Few, if any, cross-veins between apical branches of the radial sector, 



and rarely between radius and radial sector 2. 



2 Several cross-veins in middle part of fore wing beyond the 



anastomosis Acroneuria. 



Few, if any, cross-veins in middle part of fore wing beyond the 

 anastomosis 3. 



3. Ocellar triangle more than twice as broad as long ; usually one cross- 



vein between radial sector and radius, near end of latter. .Isoge?ius. 

 Ocellar triangle not twice as broad as long; only abnormally a cross- 

 vein between radius and radial sector beyond anastomosis 4. 



4. But two ocelli 5. 



With three ocelli ,. 7. 



5. Setae but little longer than width of abdomen ; the pronotum much 



broader than head Peltoperla. 



Setae much longer ; pronotum barely broader than head 6. 



6. Ocelli about one or two diameters apart ; joints of setae only one or 



two times longer than broad Neoperla. 



Ocelli four or five diameters apart ; joints of setae three to five times 

 longer than broad, often a cross-vein in anal field of fore 

 wing Atoperla. 



7. A series of cross-veins in anal field of fore wing ; a series of cross- 



veins in the cubital area of hind wings j setae not longer than 



abdomen Perlinella. 



No cross-veins in anal field of fore wing, except those to form the 

 cell 8. 



