Abdominal segment small, only slightly broader than metathorax. 

 Segment 2 with large lateral processes; the strongly convex dorsal side of 

 segments 3—7 and the ventral side of segments 3—6 with characteristic 

 single ovoid processes; ventral processes separated from segment by deep 

 constrictions; dorsal processes separated by less deep constrictions; 

 abdominal segment 7 slightly convex ventrally; segment 8 prolonged into a 

 long process which is not separated from the segment by a constriction. 

 Dorsal part of segment 9 covered by a sclerite which projects like a roof 

 above the anal legs, covering the base of the single tracheal gill (Figure 487). 



Medioanal and angle setae of abdomen not longer than half the width of the 

 head on segments 1—5; they are longer on the posterior segments (they are 

 1.25 times as long as the width of the head on segment 8); ventrolateral 

 seta on segments 1 — 7 clearly marked. Medioanal seta of sclerite of seg- 

 ment 9 longer than the others (1.66 times as long as the width of the head); 

 angle seta almost half as long; intermediate lateral seta and the anterior - 

 margin setae short and curved. 



Section "b" of the anal legs (Figure 487) broad; dorsolateral sclerites 

 of both sides contiguous in the middle; distal intermediate seta longer than 

 the others; seta of sclerite "c" small. Claw (Figure 488) very small; its 

 transverse membranous stripe broad; its distal part strongly curved; basal 

 part* with two pointed spinules directed to the end of the claw; setae 1, 2 and 

 3 longer than the others; seta 4 absent; setae 5 and 6 short, spinelike; 

 seta 7 curved; seta 8 forms a trapezoidal plate. 



Case of full-grown larva made of secretion, resembling a pumpkin seed 

 (Figure 489); anterior end of the case narrower, ending in a rounded 

 opening; a broad slit flanked with flaps in the posterior part; these flaps 

 are contiguous in their greater part; they are separated by a small opening 

 only in the middle. The larva lies in its case so that the broad surfaces 

 form the dorsal and ventral sides of the case; the ventral side of the case 

 is more convex. The lower side is directed toward the substrate and 

 pressed to the substrate by contraction of the abdominal musculature; the 

 larva lives in brooks and rivulets; its adaptation to running water resembles 

 that of other flattened rheophilic animals. 



Young larva. Length in 2nd stage 0.70 mm; width of head in 2nd stage 

 0.13 mm, in 3rd stage 0.17 mm, in 4th stage 0.23 mm, in 5th stage 

 0.27—0.33 mm. Head of young larvae broad; its anterior part is not yet 

 developed. The thoracic segments decrease in width posteriorly; 

 development of secondary setae of thorax is shown in Table 8. 



Anterior-angle setae of thorax longer than the other; medioanal setae 

 curved posteriorly. Distal seta of trochantin of young larvae situated not 

 at the end of the sclerite but slightly laterally. Ratio of length of legs of 

 young larva 80:100:115. 



Abdominal segments 1 — 8 with small single tergites in the posterior half; 

 segment 1 with a small transverse tergite anterior to the posterior tergite; 

 abdominal segment 9 completely sclerotized; its posterior part with a 

 median tracheal gill. Anal gills long (as in Orthotrichia); claws 

 without tracheal gills. 

 364 Pupa. Length 2.7—3.1 mm. Antennae short, reaching anterior margin 

 of segment 4 in male pupae, middle of segment 2 in female pupae. One 

 pair of setae near the anterior margin of the labrum; two pairs of setae 



404 



