260 



Case 20 — 22 mm long, usually made of sand grains (Figure 457, C, D, E), 

 slightly curved, rounded posteriorly, with smoother, slightly flattened, 

 ventral side; some cases consist of plant particles, as in Nemotaulius 

 punctatolineatus; dorsal wall made of large, overlapping leaf frag- 

 ments with laterall}' projecting ends; ventral wall made of similar fragments, 

 fresh or decayed, but in smaller numbers; lateral walls made of fine pieces 

 of detritus. Anterior end sometimes made like the first type; posterior end 

 like the second type. 



Young larvae (Stages 1—4). 



Stage 1 (Figure 456). Length 2.8 — 3.7 mm. Head 0.4 mm wide, yellowish 

 brown, without punctation; other sclerites lighter. Seta 1 of labrum normal, 

 pointed, not blunt and spine-shaped as in full-grown larva. 



Posterior corners of mesonotum without dark, oblique streaks. Ventral 

 elliptical areas on abdominal segments 2 — 7 absent. Gills and lateral line 

 absent. Setae of head, thorax, legs, and abdomen relatively long; some 

 setae of abdominal segments 2 — 7 are 1.5 times as long as width of head. 

 Case 3.4 — 4.5 mm long (Figure 457, A), made of coarse sand grains with 

 larger grains laterally; posterior end slightly narrower than anterior end; 

 case delicate, fragile, with a colorless, thin base of tissue. 



Stage 2. Length 4.4 — 6.9 mm. Head 0.5 — 0.6 mm wide, with indistinct 

 punctation. Seta 1 of labrum blunt but not spine-shaped. Dorsum of thorax 

 and legs with a few, secondary setae. Gills absent; abdominal segments 

 2 — 7 with ventral elliptical areas. Case made of sand grains, 4.5 — 4.8 mm 

 long; walls delicate and fragile; anterior and posterior openings sim.ilar; 

 plant fragments sometimes present at anterior opening. 



Stages. Length 5.3— 10.2mm. Head 0.8— 0.9 mm wide, dark. Meso- 

 notuna lighter than pronotum; punctation present but indistinct. 



Secondary setae on thoracic segments of P. 



n i g r i c r n i s 









Stage 





1st 



■2nd 



3rd 



4th 



Pronotum 











Anterior margin . . . 







1.3-17 



33-35 



54-59 



Others 



5 



12-13 



34-36 



64-66 



M e s n t u m 











Anterior angle .... 



1 



4-5 



8-10 



15-18 



Anterior surface . . . 



1 



1 



4-5 



9-13 



Posterior surface . . . 



.3 



4 



7-9 



16-17 



M c t a n 1 11 m 











Anterior angle .... 



1 



5 



11-12 



16-17 



Anterior surface . . . 



1 



1 



4-S 



15-21 



Posterior surface . . . 



3 



3 



7-9 



20-23 



Gills on segments 2 — 7, ventral gills only on segment 7. 

 Case 6.0— 10.0 mm long, more solidly and intricately made (Figure 457, B); 

 some cases contain, in addition to sand grains, circular or oval plant 



326 



