(478) 



770 



FIGURES 769-771. Mystacides sibiri ca Mart. : 



769 — mesonotum; 770 — tergite of abdominal segment 9; 

 771 — larval case. 



Processes and sclerites of first abdominal segment as in M. longi- 

 cornis. Gills on segments 2—7. 



Tergite of segment 9 (Figure 770) reddish brown, irregularly heart- 

 shaped, with large dark dots at anterior margin. 



Setae and anal legs as in M. longicornis. 



Case 10 — 13 mm long, straight, slightly tapering posteriorly, made of fine 

 sand grains and detritus including shells of ostracods, seeds, and large 

 fragments of trees, which project at both ends and sometimes form lateral 

 plates (Figure 771). 



Mode of life and habitats. Lakes and calm parts of rivers. 



Distribution. USSR: Eastern Siberia, Maritime Territory, and the 

 Amur Region. Not recorded outside the USSR. 



599 



