posterior margin of labrum absent. Setae of labrum, clypeus, frons and pre 

 frontal region projecting above the dorsal surface in a dense, anteriorly- 

 directed brush which is used to clean the openings at the anterior end of 

 the case. 



Mandibles with massive, broad, basal part and long geniculate apical 

 part; blade of right mandible with 3 large teeth; blade of left mandible with 

 2 large and 2 small teeth; 2 very small, blunt denticles near the apex; 

 a group of short, brown setae near the base on the ventral outer side; both 

 primary, outer setae are short, situated close together, in about the middle 

 of the mandible; 2 or 3 small thin setae near them. 



Sheaths of forewings reaching end of abdominal segment 6 or beginning 

 of segment 7. Midlegs natatorial; setae on segments 1—3 dense, those on 

 segment 4 sparse. Presegmental plates present on segments 3— 8, post- 

 segmental plates on segments 3—4; presegmental plates small, spoon-shaped; 

 denticles dark brown and large; postsegmental plates broad; plate of 

 segment 3 elliptical, concave, with numerous small denticles at the margin; 

 plate of segment 4 half elliptical, with straight anterior margin; sparse, 

 large, blunt denticles present at the posterior, curved margin; number of 

 denticles as follows: 111:7+52; IV:3 + 11-12; V:4-6; VI:5-6; VII:5; VIII:3. 



Gills pleural and ventral. Pleural gills situated on massive teat-shaped 

 pointed bases on segments 3—7; segments 3 and 7 with a small gill 

 posteriorly; other segments with 3 gills in a longitudinal row behind each 

 other; middle gill thinner and shorter than anterior and posterior gill; 

 ventral gills situated near anterior margin of segments 2 — 7, with 1 or 

 2 branches which are contiguous at the base; the branches appear 

 3 -segmented, because of the whorled arrangement of the filaments and the 

 tapering of the stalk; filaments numerous, light and long. Number of gills 

 shown in Table 16 (which gives the number of stalks and not of the filaments). 



TABLE 16 



Segment 



Pleural 



Ventral 



2 





2 



3 



1 



2 



4 



3 



2 



5 



3 



2 



6 



3 



2 



7 



1 



1 



Anal rods broad, with raised apex, forming 2 pointed posterior processes 

 of different length, so that the rod appears forked; median process larger, 

 lateral process smaller; outer side with 7 long, strong, dark brown setae; 

 a row of short setae to the base of the rod; several short, strong setae 

 ventrally, near the end of the rod; median seta thicker than the others; 

 posterior part with 9 thin, light brown setae dorsally. 



Genital appendages well marked. Genital appendages broad, bracket- 

 shaped in young male pupae; both segments indistinct in old male pupae; 

 penis sheath long, with a thick, divided end. Genital appendages of female 

 pupae consist of 2 broad, contiguous lobes. 



558 



