Primary setae of head partly reduced (Figure 584). Anterior-margin 

 setae of frontoclypeus normally developed, intermediate seta longer than 

 others, lateral seta light, curved inward; all 3 frontal setae small; anterior 

 seta situated close to intermediate seta; posterior seta smaller than others; 

 seta 7 normal, moderately long, the largest seta on the head; seta 8 short; 

 setae 9, 12, and 18 small, thin; setae 14 and 15 situated close together, short, 

 slightly smaller than seta 7; setae 10, 11, and 16 small, setuliform. 

 344 Secondary setae of head, small, light, almost procumbent. 



Number and arrangement of gills ofS. nigricornis 







2nd stage 



5± 



stage 



Segment 



dorsal 



ventral 



dorsal 



ventral 



2 



0-1 





2-3 



0-2 

 2-3 



3 



1 



1 



2-3 

 4 



3 



4 



4 



1 



1 



1-3 



4 



2-3 



4 



5 



1 



1 



1-3 



4 



2-3 



4 



6 



1 



1 (0) 



1-3 



4 



2-3 



3-4 



7 



1 (0) 



1 (0) 



1-3 



4 



2-3 

 3-4 



Labrum as in Figure 585, A; dorsal sclerite yellowish gray, sometimes 

 darker, median indentation slightly convex, not concave as in Apatania; 

 anterior margin broadly membranous, forming 2 large, lateral lobes; hair- 

 like spinules of median lobe small, situated on a tubercle in small, straight 

 tufts; hairs of lateral lobes different in size and form, some of them thin, 

 moderately long; ventral surface with feathered hairs. 



Mandibles long, almost black basally, light elsewhere; a groove divides 

 mandible into2 parts (Figure 585, B, C); mandibles flat and slightly curved 

 (more strongly curved than in Apatania); ventral blade reduced, visible 

 ventrally as an edge at lateral margin; dorsal margin with large brush; 

 chaetoids longer at margin than in middle; lateral dorsal seta moderately 

 long; ventral seta small, thin. 



Sclerites of maxillolabium (Figure 585, D) mainly yellowish brown. 

 Sclerites of cardo markedly curved, with black margin; lateral margin with 

 small setae. Setae of submentum short, situated at anterior margin of 

 median sclerite; lateral sclerites triangular, darker than median sclerites. 

 Stipes relatively wide; a large, strongly convex membranous lateral area 

 further distally; basal lateral seta short, apical seta thinner and smaller. 

 Distal seta of palpifer and median seta strong, both situated on membrane. 

 Maxillary palp short, 1st segment much larger than following segments, 

 sclerotized only ventrally and laterally; sclerite of 2nd segment also open; 



430 



