PLECOPTERA OF NORTH AMERICA 



105 



to eyes than to each other; antennae yellow at base and 

 beyond usually inf uscated ; apical segment of maxillary 

 palpi very small. 



Prothorax mostly transversely oval, i. e. the angles 

 broadly rounded ; wider than long, often one and one-half 

 to two times as wide as long; just inside the margin a 



groove which is continuous all 

 around the pronotum; surface 

 not very rugose; either uni- 

 formly yellowish or yellowish 

 with dark markings. Legs yel- 

 lowish ; usually with a narrow, 

 transverse dark band at the 

 end of the femora and the tarsi 

 usually darker toward the tip. 

 Wings yellowish or greenish 

 hyaline (much more pronounced 

 in living specimens) ; Cu2 of 

 forewing very short, originat- 

 ing at a point nearly opposite 

 the tip of the first anal vein ; 

 second anal vein of forewing 

 branched ; no cubital crossveins 

 in hind wings except the ones 

 at the end ; subcosta drops 

 down to radius a considerable 

 distance before the cord ; sev- 

 eral costal crossveins before 

 Fig. is. Aiioperia marginata the end of subcosta and one or 

 Banks - more beyond ; anal field of hind 



wings narrow but with at least two veins. 



Abdomen mostly yellowish and usually with a median 

 dorsal dark stripe which extends to the seventh or eighth 

 tergite. Cerci or tails quite long, yellowish, hairy. 



Male. Tenth abdominal tergite cleft; eighth or ninth 

 tergite often with a raised tubercle; supra-anal process 

 either upturned or recurved over the abdomen ; ninth ter- 

 gite, and sometimes eighth, medially depressed to allow 

 the supra-anal process to lie within the groove thus 

 formed ; subanal lobes small, unmodified ; ninth abdom- 

 inal sternite produced and usually somewhat truncate 

 behind, smooth below. 



Female. Hind margin of eighth abdominal sternite 

 produced into a variously modified subgenital plate. 

 Genotype, Sialis imbecilla Say. 



