Number and arrangement of gills in pupa of 

 M . longicornis 



Segment 



Dorsal 



Ventral 



2 



1 

 1-1 





3 



1 





4 



1 





5 



1 





6 





1(0) 



7 





1(0) 



Wing sheaths reaching to segment 6. Natatorial setae sparse on fore 

 tarsi, dense on mid-tibiae and tarsi. Lateral process of abdominal segment 

 1 as in Figure 764. 



Holding apparatus on abdominal segments 3—6. Presegmental plates 

 with 2—3 large spinules and sometimes also with 1—2 small spinules; 

 postsegmental plates of segment 5 with 2 rows of spines, those of the 

 anterior row larger; number of spinules 8—12. Gills on segments 2—7. 



Dorsal processes of segment 9 with 4 strong, reddish brown setae, 2 of 

 them larger than others; sometimes 1 or 2 small additional setae. Anal 

 rods thin, long (Figure 765); apical part nearly half as long as basal part, 

 narrow, hooked apically; a median process with large, sharp, light spinules 

 between basal and apical parts; small spinules further basally, and at the 

 median margin in apical part; setae situated near middle and on hooked 

 apex of the rod. 



Case 10— 14 mm long, attached at each end by a large ventral disk, 

 sometimes with 2 additional, smaller, lateral disks posteriorly. 



Mode of life and habitats. Vegetation of lakes and slow rivers; 

 feeding on algae. 



Distribution. The European USSR; Western and Eastern Siberia. 

 In addition, Europe. 



5. Mystacides nigra Linne 



Pictet, 1834:Plate XI, Figure 4.— Hagen, 1864:232.— Meyer, 1867:158.— 

 Klapalek, 1893:95— 99, Figure 26. — Struck, 1903 :Plate III, Figure 8.— Ulmer, 

 1903:105, Figure 119. — Thienemann, 1904b:261, Figure 17; 1905b:Figure 79. 

 Siltala, 1905:88—91.— Ulmer, 1909 :249, 311, Figures 375, 376c, 457a. — 

 Lestage, 1921:618—623, Figures 208 k, m, o, 209b, 211b.— Lepneva, 1940:211.- 

 Hickin, 1943:69— 71, Figures 1—11. 



595 



