normal length. Claw (Figure 471 ) short; the basal section is separated by 

 a transverse stripe, which is massive and broad; end of claw thin and 

 strongly curved. Seta 8 on the claw thin and curved in the early stages; 

 seta 7 long, as long as the ventral seta of the basal part. The young larvae 

 have three caudal tracheal gills; gills of live specimens silver-colored; 

 median gill situated on the posterior margin of the dorsum; lateral gills 

 on the distal end of the basal part of the anal legs (Figures 470 and 471). 



Pupa. Length of male pupae 2.7 mm, of female pupae 2.9 mm; antennae 

 of male pupae reaching middle of segment 7; antennae of female pupae 

 reaching posterior margin of segment 3; the pointed wing sheaths reach the 

 posterior end of the body in both sexes. Labrum with slightly convex, 

 almost straight anterior margin (Figure 4 72) and with two pairs of short 

 setae; 2 short median setae and 2 long lateral setae near the posterior 

 margin. Mandibles short and massive (Figure 473); their distal part 

 serrated; the straight basal seta is situated near the base; seta anterior to 

 it short and curved. The natatorial setae are situated dorsally and 

 ventrally on segments 1 and 2 of the mid-tarsi. Presegmental plates 

 (Figure 4 74) oblong, oblique; postsegmental plates shorter and pear-shaped; 

 both types of plates with a longitudinal row of spines. Number of spines: 

 111:6-9+2-5; IV:7-9+2-5; V:6-9+2-4; VI:7-13; VII:7-12; the difference 

 in the size of the spines is smaller than in the preceding genera. 



Pupal case slightly prolonged at both sides with thin, light plates woven 

 by the larva at the anterior and posterior end; dorsal sides of plates 

 contiguous in the middle (Figure 476); ventral sides of the plates diverging 

 and fused with the disk attached to the substrate (the disk consists of thin, 

 radial filaments); ends of case closed with a thin membrane. 



Mode of life and habitats. Lakes and slowly running rivers in 

 the plains; in plant thickets. 



Distribution. European USSR. In addition, Europe, Iran, recorded in 

 Africa. 



6. Genus Ithytrichia Eaton 



Full-grown larva. Length about 3 mm. Head slightly flattened dorso- 

 ventrally, narrower anteriorly; frontoclypeus large; gula fused with the pre- 

 gula. Eyes situated at midlength of head; sensilla of antenna long, with a 

 seta at the base. Posterior frontal setae long, curved to the surface of the 

 sclerite; seta 9 longer than the others; setae 17 widely separated. 



Labrum oblong, without a median notch on the membranous margin. 

 Mandibles flattened; right mandible without a lower blade; left mandible 

 with a rudimentary lower blade in the distal part. 



Nota of thorax with numerous short, soft secondary surface setae in the 

 anterior half. Horn of trochantin long. Prothorax with two fused posterior 

 sternites; meso- and metathorax with one median sternite. Forelegs 

 without basal process of femur and without apical process of tibia; midlegs 

 and hind legs with long tarsi and massive claws. Abdomen laterally 

 compressed; abdominal segment 2 with lateral processes; segments 3—6 

 with dorsal and ventral sucker-shaped appendages; a similar appendage 



399 



