indistinct, in contrast to M. azurea. Anterior pair of the 6 dots on 

 frontoclypeus large, with a dark, transverse connection, even in dark 

 speciraens; 2nd pair smaller than 1st; pale 3rd pair indistinct; the group 

 in posterior part formed by a row of 4 dots and 3 fused dots anterior to them; 

 lateral dots smaller than median dots, sometimes absent. Dorsal stripes 

 narrow, pinkish anteriorly, represented posteriorly by 3 large, distinct, 

 brownish dots along frontal sutures; 2 rows of similar dots on each side on 

 light background along coronal suture; lateral stripes replaced by 3 rows of 

 distinct dots; ventral surface with 6 small dots on each side near occipital 

 foramen. Gula brownish (Figure 754, B). 



Pronotum and mesonotum whitish, lighter than head. Pronotum (Figure 

 755, A) with an indistinct, white stripe separating anterior angle; posterior 

 margin, grayish, narrow laterally, reddish brown. Median and lateral stripes 

 of mesonotum (Figure 755, B) indistinct, pale grayish. Dots and setae as in 

 M . azurea. Legs as in M. azurea; distal spots of hind tibia and tarsus 

 reddish bro-vvn, larger than in M. azurea. 



Gills absent. Tergite of segment 9 with a pinkish brown area; setae 

 situated at whitish margin, as in M. azurea. Anal legs as in M. azurea, 

 area "b" with distinct, pinkish brown, dorsal dots. 



Case straight, slightly tapering posteriorly, made of small, usually flat, 

 pieces of detritus and sand grains, often with platelets of mica, with large 

 pieces of detritus, small rods, or conifer needles projecting at both ends 

 (Figure 756). 



Lepneva (1949:169) assumed that larvae of M . dent at a are indistinguish- 

 able from those ofM. azurea. The differences in coloration just described 

 permit easy differentiation. 



Mode of life and habitats. The Siberian species is vicarious and 

 isoecological with the European M. azurea. It occurs on silt-sand bottom 

 in lower littoral and sublittoral of mountain lakes; at a depth of 10.0 — 20.0m 

 in Lake Teletskoe; at a depth of 4.0— 11.0m in Lake Nizhne Mul'tinskoe. 



Distribution. USSR: Altai, Say ans. Not recorded outside the USSR. 



4. Mystacides longicornis Linne 



Meyer, 1867:159.— Klapalek, 1886:42—45, Figure 15.— Struck, 1900:Figure 

 41; 1 903 :Plate III, Figure 7. — Ulmer, 1903 :1 05, Figure L. — Thienemann, 

 1904b:261, Figure 18; 1905b:534-535, 552, Figures 75,78- Siltala, 1905:71-74, 

 Figure 18.— Ulmer, 1909 :279, 31 1, Figure 457b.— Lestage, 1921:618—623, 

 Figures 208—211.— Lepneva, 1940:21 1, Figure 3.— Hickin, 1953:114—116, 

 Figures 3—6. — Yamamoto and Wiggins, 1964:1 108— 1 110, Figures 5,11. 



Fvill-grown larva. Length 8.5— 11.3 mm. Body cylindrical; mesothorax, 

 metathorax, and following abdominal segments almost equally wide. Main 



471 coloration light yellow; pattern distinct, formed by black and dark brown 

 stripes and spots. Head (Figure 757, A) large; sensilla of antenna light, 

 almost transparent. Frontoclypeus with 3 pairs of dark dots at anterior 

 margin; first 2 pairs indistinct in dark specimens, situated on a dark, 

 transverse stripe as in M . nigra, but 2nd pair of dots remains visible; 

 dots of 3rd pair small, indistinct, situated between intermediate frontal setae; 

 posterior part of sclerite with a wide, black band behind a deep median 



472 indentation and before a process. Dorsal stripes black, distinct, close to 

 frontal sutures; wide dark stripes lateral to coronal suture. Lateral stripes 



590 



