setae dorsally at distal margin, median distal and neighboring seta long, 

 thicker, and darker than others; only one seta of moderate length near 

 median margin subapically close to median distal seta; ventral seta short, 

 thin, light. Sclerite "c" brown, wide, narrower basally, with a small, light, 

 basal seta. 



Claw (Figure 630, B) of characteristic form, strongly convex basally, with 

 pointed, reddish apex with 2 large, dorsal denticles; 2 parts divided by narrow 

 suture; seta 1 situated in basal part, short, brown; seta 2 thin, light, 

 moderately long, situated dorsally above suture; seta 3 similar, situated 

 dorsally in distal part; seta 6 situated laterally near end of suture, shorter 

 than 2; setae 7 and 8 situated ventrally in basal part, short, light, spine - 

 shaped; seta 5 minute, situated lateral to seta 8; seta 4 situated medially, 

 slightly larger, both light, very thin. 



Case 10—12 mm long (Figure 63 1), in form of straight tube, slightly 

 narrower posteriorly, usually tetrahedral, made of secretion and covered 

 with regular, narrow, transversely arranged, pieces of detritus; edges 

 sometimes smooth or case with round cross section, and made in part or 

 entirely of secretion; case attached at anterior end, lies against the current 

 (see Vol. II, No. 1, p. 121). Sometimes a large number of cases in one place. 



Pupa. Length of male pupae 8 mm; female, 9.0— 10. 5 nam; antennae of 

 male pupae reaching middle of segment 8, those of female, segment 6; scape 

 with short, light setae. 



Labrum narrower anteriorly, with slightly projecting median part; seta 1 

 situated at anterior margin, short, thin, light, other 5 setae strong, yellowish, 

 large, forming 2 rows on a light area; anteclypeus with 2 strong, large setae 

 and a smaller, light, lateral seta. Mandibles with wide base and a narrow, 

 long, slightly curved, distal part with serrated median side; lateral setae 

 strong, yellowish brown, dorsal seta slightly larger than ventral. 



(377) 



Number and arrangement of gills of the pupa ofB. subnubilus 

 (after Siltala) 



Segment 



Dorsal 



Pleural 



Ventral 



2 



5-6 





1 



3 



6 



1 



1 



4 



3-6 



1 



1 



5 





1 



1 



6 





0-1 



1 



Sheaths of fore wings reaching beginning of segments 5—6, those of hind 

 wings shorter. Fore and mid-tibiae and tarsi with natatorial setae, dense 

 on midlegs, sparser on forelegs. 



Abdominal segment 1 brown dorsally near posterior margin, saddle- 

 shaped, with 2 darker, lateral elevations with small, black spinules; holding 

 apparatus of segments 3—7 represented by small elliptical, presegm.ental 



471 



