Stagnant water 



Integripalpia predominate in stagnant ponds; Annulipalpia are represented 

 by a few species of Hydroptilidae and Polycentropodidae and have a 

 secondary position. 



Lakes. The character of the biotopes of lake bottoms and of their 

 population is determined by the soil of the bottom, the food available and 

 the condition of the water; very mobile (in the surf zone), slightly mobile 

 (in plant thickets and in the sublittoral) or almost stagnant (in the region of 

 silt deposits, the profundal region). 



Conditions in parts of the open stony littoral resemble those in mountain 

 streams and brooks; there is the same rocky, boulder-covered bottom or 

 bottom formed of stone fragments, with rich food in the form of detritus 

 algae and microflora, and with numerous biotopes suitable for bottom 

 animals, including caddis fly larvae. In the sandy littoral the larvae 

 remain at a certain depth if the silting is weak and there is plenty of 

 detritus and little mobile water; in plant thickets, the larvae crawl on 

 plants, swim among stalks and leaves and live among plant remains on the 

 bottom. 



In the north and northwest of the European USSR, in the large oligotrophic 

 lakes of Karelia (Ladoga, Onega, and Segozero), one frequently finds 

 rheophilic species which occur also in brooks and streams, in biotopes in 

 the stony littoral, especially Rhyacophila nubila, Hydropsyche 

 angustipennis, H.pellucidula, Polycentropus flavomacu- 

 lauts and Potamophylax s t e 1 la t u s, and also Apatania w alien - 

 greni, Leptocerus cinereus, L. excisus, L. annulicornis, 

 Chaetopteryx sahlbergi. In parts with a moderately strong surf, 

 Leptocerus aterrimus, Goera p i 1 o s a and Lepidostoma 

 hi r turn occur; in overgrowths of diatoms one commonly finds larvae of 

 126 Le pt o c e r u s fulvus and L. senilis. The species Molanna 



(M. angustata, M. palpata, M. submarginalis), Molannodes 

 tincta, Mystacides azure a, Anabolia soror, Oecetis ochra- 

 cea and Oe.lacustris are characteristic for biotopes of the sandy 

 littoral, at a depth of 0.5 — 1.5 m. In plant thickets one constantly finds 

 Hydroptilidae (Agraylea multipunctata, Oxyethira distinctella, 

 O. costalis and Orthotrichia tetensii); Cyrnus flavidus and 

 Holocentropus picicornis are common in plant thickets; Triaeno- 

 des bicolor and Mystacides longicornis (Leptoceridae) are 

 common; Leptocerus aterrimus is common; Phryganea striata, 

 Agrypnia obsoleta, A. pagetana, rarely A . v a r i a ( Phryganeidae) 

 are common. Among the Limnophilidae, one regularly finds Nemotaulius 

 pu n c t at ol i n e a t u s, G r am m o m ot au 1 i u s atomarius, Limno- 

 philus nigriceps, L. decipiens, L. politus, L. rhombicus, more 

 rarely L.borealis and L. f 1 a v i c o r n i s; the species of Molanna and 

 Oecetis, found in the sandy littoral, occur also on the weakly silted bottom 

 of open plant thickets. These species, and also Cyrnus flavidus and 

 Mystacides a z u r e a, occur regularly in the sublittoral; isolated speci- 

 mens occur in the profundal zone to a depth of 10— 20m (Lepneva, 1928:115; 

 Sokolov, 1956:79-87; Gerd, 1949:48-83). 



In the mesotrophic and eutrophic lakes of the leveled glacial landscape 

 of the Baltic and Leningrad regions and the Valdai Upland, an open surf 



118 



