7. Genus Oligostomis Kolenati 



Full-grown larva. Length 2 0— 2 3mm. Dark median pattern on fronto- 

 clypeus absent; seta 17 on head shorter. Mesonotum with 2 small, median 

 sclerites near anterior margin. Gills on segments 1—7. 



Case made of fragments of plants arranged in rings. 



Pupa. Length 19 mm. Frontal sclerite with small anterior process. 

 Distal end of mandibles rudimentary. Gills present on abdominal segments 2—7. 



Mode of life and habitats. Running, peaty, water bodies. 



Distribution. Northern, central, and western parts of the European 

 USSR. In addition, Central and Northern Europe, Japan, North America. 



1. Oligostomiis reticulata Linne 



Struck, 1903:59-65, Plate I, Figure 5. Plate VII, Figures 14, 15, 16, 19, 20, 

 22.- Siltala, 1903a:4-6, Figure 1. - Ulmer, 1903:41, Figure 93.- Siltala, 

 1904c:6.- Ulmer, 1909:238, 302, Figures 365,459c.- Lestage, 1921: 

 555-558, 572-579, Figure 192. - Lepneva, 1940:208, Figure 8. 



F^lU -grown larva. Length 20— 23mm. Ground color of sclerites yellow, 

 in some places brownish yellow; pattern distinct, brownish. Head 

 (Figure 88) slightly oblong; frontoclypeus wide anteriorly, its posterior 

 part much smaller than the rest; 4—5 dark dots forming a transverse 

 row, median dots sometimes lighter; middle with 2 dark dots on each side. 

 Wide, dark, dorsal stripes from the anterior margin; they separate 

 posteriorly close to the frontal sutures, so that the posterior angle is light or 

 they fill the posterior angle; in the latter case, the pattern is U-shaped, which 

 is characteristic for the genus; a few, large, lighter dots on the stripes; 

 lateral stripes wide, chestnut brown, less dark than the dorsal stripes, 

 distinct, with numerous dots; similar small dots on light background 

 between the dorsal and lateral stripes; ventral side of head almost entirely 

 chestnut brown, with several indistinct large dots. 



Lateral anterior -margin seta (Figure 88) short, light; median seta 

 slightly larger, dark; intermediate seta thicker and darker than median 

 seta; frontal setae dark, anterior one small, situated near the stripe, 

 middle seta long, closer to frontal suture, posterior setae slightly longer 

 than middle seta, situated near suture. Setae 9 and 11 situated on a 

 large, light spot, seta 9 long, dark brown, seta 11 thin, as long as middle 

 frontal seta; seta 7 longer and thicker, seta 10 short, straight, light; seta 

 12 situated laterally on light background, almost as long as 9; seta 13 dark, 

 small; seta 14 situated in a light indentation of the dorsal stripe, thick, 

 longer than other setae; setae 15 and 16 short, thin; seta 17 situated on a 

 large, light dot, less long and thin than in the other genera, brown, markedly 

 shorter than seta 14. Ventral seta 8 small, thin, spiniform; seta 18 slightly 

 smaller, situated on light spot (Figure 89). 



Labrum (Figure 90) reddish brown, without pattern; median depression 

 with 5—6 tubercles anteriorly; seta 1 inconspicuous, small, procumbent; 

 seta 2 in form of light, blunt spine; seta 4 situated on margin of depression, 

 light, tapering, crossed; setae 5 and 6 larger than in Phr y gan ea, dark 

 brown; seta 3 smaller and lighter. 



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