441 



Abdomen slightly tapering posteriorly; segments 2—3 largest, equally 

 wide; segment 9 wide but shorter than segment 8. Abdominal segment 1 

 with wide dorsal process and large, strong, medioanal setae at anterior 

 margin; lateral processes displaced to ventral side in form of elliptical 

 plates covered with light spinules, and situated at anterior margin of dark, 

 brownish, curved sclerites with 2 pleural setae at distal margin. Lateral 

 line on segments 3—7 in form of a narrow, white stripe with small grayish 

 hairs, a row of dots with 2—3 light, minute spinules on segment 8. Gills 

 with several short, whitish filaments dorsally on segments 2— 3, pleurally 

 on segments 1—2 and ventrally on segments 1—3. 



Tergite of segment 9 chestnut brown, with a narrow, yellowish stripe at 

 posterior margin (Figure 706, A); anterior-margin setae thin, long, close 

 to medioanal setae, which are longer and thicker, dark brown; intermediate 

 seta small, light; lateral and anterior-angle seta situated close together, 

 similar to the anterior-margin seta. 



Anal legs short, massive, with 2 large, membranous, basal folds around 

 anal slit, and with small, light spinules on ventral side, Sclerite "b" dark 

 brown, covering anal leg dorsally, laterally, and ventrally by curving around 

 sclerite "c"; 4 thick, dark setae of different length, and a small, light seta 

 dorsally near loargiii, a similar dark, thin, moderately long seta laterally; 

 ventral seta small, brown, thin. Sclerite "c" in form of a light brown plate 

 with a thin seta. 



Claw reddish brown, small, with a large dorsal denticle, sometimes with 

 an additional smaller denticle (Figure 706, B); setae 1 and 2 small, light; 

 seta 6 situated subdorsally on side, thick, long; seta 3 situated medially, 

 thin; seta 4 larger and thicker; seta 5 small, sitiiated near membranous 

 stripe; setae 7 and 8 situated ventrally, small. 



Case conical, curved, 15— 16 mm long (Figure 707); longer cases of 

 full-grown larvae consist of 2 parts, a posterior part made of fine sand 

 grains and probably made in stage 2 or 3, and an anterior part, which forms 

 the greater part of the case, appears later and consists of larger sand 

 grains; posterior end disappears at end of stage 5, and the case is only 

 slightly longer than the body before pupation. 



Number of gill tufts ofA.aterrimus 



Segment 



Dorsal 



Pleural 



Ventral 



1 





1 





2 



1 

 1 



1 

 2 



1 2 

 1 1 



3 



1 





1 1 



Pupa. Length 8 — 12mm. Antennae of male pupae coiled 4 times around 

 posterior end of body, those of female twice. Labrum with rounded sides and 

 with a teat-shaped median process; setae short, reddish brown. Mandibles 

 (Figure 708) with concave, serrated, median margin; lateral setae short, 

 ventral setae smaller than dorsal. 



552 



