PERLA. 23 



margined with yellow ; feet yellow, a fuscous ring upon the femora 

 at base, knees, tibia) externally and tarsi fuscous ; abdomen above 

 brown, segments margined with yellow ; beneath yellow, middle of 

 the base obscure ; setce yellow at base (the remainder is broken 

 off) ; 9 antepenultimate ventral segment, middle lobe, short, broad, 

 rounded, infuscated ; wings grayish-subhyaline, costal margin a 

 little yellowish, veins testaceous. (Female.) 



Length to tip of wings 18 millim. Alar expanse 34 millira. 



Hob. Washington (Osten Sacken, 1857). Is this P. capitata 

 Pictet ? 



16. P. postica ! 



Perla postica. Walker Catal. 144, 11. 



Black ; head equal to the prothorax, black, a spot upon the 

 occipital middle, which is hastlform and sometimes two anteriorly 

 orange-yellow ; antennas black ; prothorax transverse, quadran- 

 gular, short, black, rugulose, an orange stripe upon the middle, 

 sides straight, angles acute ; feet brownish-black ; abdomen black, 

 beneath in the middle yellowish ; setre black ; J^ last ventral seg- 

 ment larger, ovate, fuscous ; 9 antepenultimate segment large, 

 triangularly ovate, fuscous ; wings grayish-subhyaline, veins fus- 

 cous. 



Length to tip of wings 15 — 20 millim. Alar expanse 28 — 34 

 millim. 



Hah. Louisiana (Schaum); Mackenzie River (Richardson). 



I do not know whether this is the same with Walker's species 

 or not. It is some time since I examined his specimens in the 

 British Museum. 



The words in Mr. Walker's diagnosis, "prothorax produced into 

 an acute angle, or short horn on each side by the foreaugle," are 

 erroneous, and they are accordingly omitted here. 



17. P. olivacea! 



Perla olivacea Walk. Catal. 144, 12. 



Fuscous ; head hardly broader than the prothorax, fuscous, ful- 

 vous in front with a large occipital, trilobed, transverse spot ; an- 

 tenna) fuscous, fulvous at base ; prothorax transverse, quadrangular, 

 shorter, fuscous, rugulose, a broad, yellow middle stripe ; sides 

 straight, anterior and posterior margin a little rounded ; the feet 

 fuscous, beneath and tibia? luteous ; abdomen fuscous; seta) luteous, 



