Third stage. Length 4.5 — 7.5 mm, ratio of length of head, thorax and 

 abdomen 10:24:62 (10:35:99 in the full-grown larva). Dorsal stripes appear 

 near the pattern of the frontoclypeus. Labrum with a median pit. Sternite 

 of prothorax complete with 2 sclerites posteriorly. Ventral gills more 

 numerous (Table 19), most of them branched. 



Fourth stage. Length 7— 10 mm. Form of body, pattern of head and 

 thoracic sclerites as in the full-grown larva; secondary chaetotaxy abundant. 

 Pleural gills absent; number of filaments of ventral gills shown in Table 19. 



Pupa. Length of male pupae 8—11 mm, of female pupae 10.0—12.5 mm. 

 Antennae of male reaching end of body, those of female reaching abdominal 

 segments 7—8. Labrum about half as long as wide; tufts black. Right 

 mandible with 3 teeth in addition to apical tooth; left mandible with 4 teeth, 

 the 2nd from the apex small; blades of mandibles finely serrated between 

 the teeth. 



Sheaths of fore wings reaching segment 4; sheaths of hind wings reaching 

 segment 5; natatorial setae of mid-tarsi dense, present on segments 1—4 

 in female pupae, on segments 1—3 in male pupae; 4th segment with only 

 sparse setae or with none. 



Presegmental plates present on abdominal segments 3—8, postsegmental 

 plates on segments 3—4; number of spinules as follows: 111:5—11; IV:3— 6 + 

 7-19; V:4-8; VI:4-8; VII:5-7; VIII:4-7. Conical pleural gills present on 

 abdominal segments 4—7, ventral gills on segments 2—7; number of filaments 

 in ventral gills shown in Table 20 (after Siltala). 



TABLE 20 



Segment 



Lateral 



Median 



2 



20-27 



19 



3 



21-28 



19-28 



4 



18-25 



19-20 



5 



17 



13 



6 



10 



11-13 



7 



4-12 



8-10 



Anal rods longer than in H. ornatula; setae black. Genital appendages 

 of male bracket-shaped, with smooth, curved median margin. 

 497 Length of case 10—17 mm, made of small stones, sand grains or plant 



fragments; if made of plant fragments, the case has irregular form; surface 

 of case sometimes irregular; cases sometimes are found in large numbers 

 close together. Membrane at anterior margin with openings (Figure 698). 



Mode of life and habitats. Larvae predacious, feeding on small 

 benthic animals, mainly insects (especially larvae of Tendipedidae); they 

 occur in brooks and rivulets with clean cool water and build capturing nets 

 among stones or pieces of wood (see pp. 77, 78). 



Distribution. North, west, and central belt of the European USSR. 

 In addition, Europe. 



567 



