570 



Lciif^th of abdomen, i 25 mm. 



Length of alidomcn, 9 25 mm. 



Length of hind wings, 3 .27 mm. 



Length of hind wings, 9 28 mm. 



Width of hind wings, 6 3.5 mm. 



Width of hind wings, 9 3.5 mm. 



This species has not been taken in IIHuois, but has been collected 

 in Indiana by Mr. Williamson, and the above description has been 

 made from specimens in his collection. 



IscHXUR.\ I'OSiTA (Hagen) 



Nymph. — Color, usually dark brown. 



Head oval or elliptical in outline, the caudo-lateral angles not pro- 

 jecting and with only a few setae; antennae of the usual form, the 

 hrst two segments dark in color, the second light at the tip; labium 

 extending between or slightly caudad of the procoxae; mental setae 

 four and sometimes a small fifth on each side ; lateral setae five ; lateral 

 marginal setae of the median lolje four. 



Tiiorax about ecjual in diameter throughout; femora with rows 

 of setae which become heavier towards the apices ; tarsi pale, the apices 

 of the third segments brown; metathoracic wing-cases extending cau- 

 dad to the fourth abdominal segment. 



Abdomen : cuticle provitled with numerous black spots usually 

 bearing a single minute seta; lateral keels without setae except those 

 of the caudal segments ; gills lanceolate ( Figs. 64, 66) , broadest beyond 

 the middle, usually with four crescentic brownish bands of wiiich the 

 apical ones are somewhat paler than the proximal, the median gill w ith 

 a dorsal row of about fourteen setae extending one-third the length 

 of the gill from the base ; ovipositor extending to the apex of the tenth 

 abdominal segment. 



Measurements 



Length 1L5 mm. 



Length of abdomen '7.5 mm. 



Length of gills 5-5.5 mm. 



Width of gills 1.6 mm. 



Length of metathoraeie wing-cases. .3.0 mm. 



Length of median lobe 2.0 mm. 



Width of median lobe 5-1.6 mm. 



The nymph is very closely related to vcrticalis but may be sep- 

 arated from the latter by means of- the shape and figuration of the 



I 



