Case 15—16 mm long, made of sand grains, relatively wide, with smooth 

 walls, curved, only slightly tapering posteriorly, end truncate; posterior 

 opening wide, with a dark membrane only at margin (Figures 873, B, C). 



Pupa. Length 10.5 — 11 .0 mm. Antennae filiform, reaching end of body; 

 proximal segment much thicker and longer than others. Two blunt processes 

 above labrum. Labrum small, its form as in S. p e d e m. ont a nu m; setae 

 of anteclypeus shorter than on labrum, as in S.pedemontanum. Mandibles 

 large, with long, curved, distal part with coarsely serrated median side. 



Wing sheaths reaching to end of segment 7. 



Holding apparatus with following number of hooks: segment 111:2; 

 segment IV:2-3; segment V:2-3+ 2-3; segment VI: 2-4; segment VII: 2-3. 

 Lateral line with dense, brown setae on segments 5 — 8. Gills on segments 

 2-8. 



Anal rods slightly curved. Genital appendages broad, longer than penis 

 sheath. 



Case as in larva, made of sand grains, 16—18 mm long, with coarser 

 grains at anterior margin; anterior and posterior membranes with a slit- 

 shaped hole. 



Mode of life and habitats. Brooks and rivulets with a rapid 

 current; estuaries of lakes. 



Distribution. Western and northwestern parts of European USSR. 

 In addition, Europe. 



3. Sericostoma grusiense Martynov 

 Meshkova, 1964:67-71, Figures 1-6. 



Full-grown larva. Length 11 — 12 mm. Head (Figure 876, A) uniformly 

 dark reddish brown, dorsally with indistinct, large, dark dots in posterior angle 

 Q of frontoclypeus and lateral to epicranial suture. Ventral side with dark 

 areas laterally like dorsal side, with large, light dots; gula brownish, 

 darker anteriorly, clearly marked off by a light stripe (Figure 876, B). 



Pronotum with small, pointed processes at anterior angles; anterior 

 part of surface brown, with numerous setae, posterior part lighter, 

 brownish, with indistinct, darker brown spots, posterior margin yellowish. 



Mesonotum brownish, whitish posteriorly, with indistinct dots. 



Propleuron brown, with dark brown pleural suture. 



Legs brown; secondary setae of mid- and hind legs numerous on coxae 

 and femora, sparse on tibiae. 



Case 12—15 mm long, in form of a wide, slightly curved tube with a 

 smooth surface of fine, uniformly arranged sand grains; posterior membrane 

 with large, round, central hole. 



Pupa. Antennae of female pupae reaching end of body, antennae of male 

 pupae slightly longer. Wing sheaths reaching to abdominal segments 6—7. 

 Sclerites of holding apparatus presegmental on segments 3—7, postsegmental 

 on segment 5; denticles large, 2 on presegmental sclerites, 2—4 on 

 postsegmental sclerites. 



Pupal case slightly smaller than that of larva, 10 — 11 mm in male pupae, 

 11— 12 mm in female pupae, often occurring in groups of to 200 specimens 

 (Figure 877). 



684 



