Wing sheaths pointed, reaching end of abdominal segment 5. Natatorial 

 setae on mid-tarsi and proximal segment of hind tarsi. 



Abdominal segment 1 with 2 dark. 



Number and arrangement of gills ofL. obscurus 



Segment 



Dorsal 



Ventral 



2 



3 



3 



3 



3 



4 



3 

 3 



4 



2 

 4 



3 



4 



5 



2 

 4 



2 



4 



6 



2 



4 



2 



4 



7 



2 



4 



2 

 4 



Mode of life 

 Distribution 

 Europe. 



and habitats. 



Western part of European USSR 



blunt tubercles with small denticles. 

 Holding apparatus on segments 3—7 

 presegmental in form of small, 

 rounded sclerites with denticles 

 directed posteriorly; numbers as 

 follows: 111:1; IV:2; V:2-3; VI:2; VI1:2; 

 segment 5 with an elliptical plate with 

 numerous spinules directed anteriorly. 

 Lateral line from end of segment 5 

 to segment 8, formed by dense, strong, 

 moderately long, grayish brown 

 setae. 



Gills dorsally on segments 2—4, 

 ventrally on segments 2—7. Anal 

 appendages in form of thin rods 

 curved inward at end (Figure 595). 

 Posterior opening of case, as in 

 Goer a and S il o, with a membrane 

 with small, oblong, radial, marginal 

 slits (Figure 596). 

 Brooks; feeding on detritus. 



In addition. 



2. Lithax incanus Hagen 



Sykora, 1960:217-224, Figures 1-8. 



Number and arrangement of gills of pupa of 

 L. incanus 



349 



Segment 



Dorsal 



Ventral 



2 



2 



1 

 2 



3 



2 



4 



3 



4 



4 



2 



4 



2 

 3 



5 



2-3 



4 



3 

 3 



6 



3 



4 



3 

 3 



7 



3 

 4 



3 

 3 



8 



1 





Full-grown larva. Length 9— 10 mm. 

 Body less tapering posteriorly than Silo. 

 Head as in Figure 597. Transverse 

 ridge in middle of head distinct, covered 

 with wart- shaped tubercles, of which the 

 lateral are larger; surface anterior to 

 ridge brownish; posterior blackish brown; 

 occipital area yellowish, with large, dark 

 dots; entire surface of head with large 

 or small tubercles. Secondary setae 

 present (Sykora, 1960:233). 



Labrum, with broadly membranous 

 anterior and lateral parts; sclerite 

 brown, yellowish brown at the anterior 

 margin. Mandibles (Figure 598) black, 

 with rounded apex; dorsal blade pro- 

 jecting, with tubercles in some places; 

 brush small, situated submarginally on 

 dorsal side and formed by fine chaetoids. 



435 



