Wing sheaths reaching segments 6—7. Fore tarsi with sparse setae, mid- 

 tarsi with dense natatorial setae. 



Notum of 1st abdominal segment with small, sclerotized processes with 

 denticles at posterior angles. Holding apparatus on segments 2 — 6, 

 postsegmental plates on segment 5. Gills with a single filament or absent. 

 Lateral line thin, with fine, grayish setae on segments 3—8. Lateral processes 

 of segment 9 with 4 short, dark setae. Anal rods long, thin, apical part much 

 larger than basal part, with curved or hooked apex. 



Case attached at both ends by large disks; membrane with wide, round 

 hole. 



Mode of life and habitats. Stagnant, or slowly running water, 

 among vegetation; some species occur on a bottom of sand and detritus or 

 silt and detritus in littoral or sublittoral of large lakes. 



Distribution. The European USSR, Western and Eastern Siberia, 

 Maritime Territory, the Amur Region. In addition, Europe, Asia, North 

 America. 



Key to Species 

 Full-grown larva 



1 (6). Head pattern consisting of dots; dark stripes short, sometimes 



indistinct or absent; gills absent. 



2 (5). Head with bright pattern of large dots; dorsal stripes narrow 



anteriorly, dark and distinct or less distinct; groups of dots lateral 

 to gula. 



3 (4). Frontoclypeus with 3 pairs of dots anteriorly, dots of posterior pair 



small, indistinct, pale; dots of anterior pair large, closer together, 

 sometimes completely covered by a dark transverse stripe; 

 dorsal stripes distinct in dark specimens, dark anteriorly, pale in 

 middle and posteriorly; mesonotum uniformly slightly dark in 

 middle; Europe 1. M. azurea L. (p. 581) 



4 (3). All 3 pairs of dots in anterior part of frontoclypeus large, distinct, 



bright; a 4th, darker pair near curvature of frontal sutures; 

 frontoclypeus without dark, anterior, transverse stripe; dorsal 

 stripes indistinctly dark only anteriorly, in form of dots posteriorly; 

 mesonotum with a short, reddish brown stripe in anterior part, and 

 reaching a short, similar stripe at anterior margin; East Siberia 

 2. Mystacides sp. (p. 587) 



5 (2). Head pattern with dots only, without dark areas; dots small but 



distinct, pinkish brown; Siberia 3. M. dentata Mart. (p. 588) 



6 (1), Head with characteristic, H-shaped black pattern formed by dorsal 



stripes and band in posterior part of frontoclypeus; first pair of 

 dots in anterior part of frontoclypeus, large or covered by a wide, 

 black, transverse stripe; dots of 3rd pair indistinct, small, or absent; 

 gills present. 



7 (10). Stripes of H-shaped pattern, at coronal suture, and lateral stripes 



wide, occupying most of dorsal surface. 



8 (9). Black transverse stripe not always present near anterior margin; 



ventral side with groups of dots; gills on segments 2—7 



4. M. longicornis L. (p.590) 



580 



