The thermal conditions of the water bodies of spring regions in lowland 

 and plain landscapes inhabited by stenothermal species closely resemble 

 those in mountain landscapes, as for instance in water bodies fed by under- 

 ground sources on the Silurian plateau of the Leningrad Region.* In such 

 springs and brooks, the larvae of species of A p at an i a (A. z on el la, 

 A. wallengreni) occur at a temperature of 5—13°; in aquaria they 

 tolerate a temperature of 14—15°; the larvae of Potamophylax 

 stellatus and Chaetopteryx sp. live in summer in springs at a 

 temperature of 5.4—6.5°; in the brooks and streams issuing from these 

 springs, they live at temperatures to 14°; larvae of Rhyacophila 

 s e pt e nt r i on i s were found in summer at temperatures of 5— 16°; the 

 larvae of Rh. nubila and Hy droptila maclachlani were found at 

 a summer temperature of 11 — 16° (Lepneva, 1930:283). 



In the Nakhodna brook (Kalinin Region) Rhyacophila nubila larvae 

 were found in the short summer also at 18.8° on 5 July 1951. 



In the Altai, the stenothermal species Ecclisomyia digitata 

 (Praecosmoecus digitatus) lives in springs with a temperature of 

 8.5° and in the open littoral of the cold-water Lake Teletskoe; the 

 temperature in this lake fluctuates from 3—6° in May and June; during the 

 short summer (on windless days) it fluctuates from 10—12° in August; 

 however, when the wind drives the warm surface water to the open lake, 

 the temperature falls again (sometimes to 7—8°). 



The widely used definition of a large group of species as cold-water 

 stenothermal species is thus justified only because it stresses that this 

 group is restricted to water bodies or to parts of water bodies with a low, 

 or relatively low, summer water temperature, and also that these species 

 108 are absent in warm water bodies; a number of stenothermal species can 

 tolerate the short period of high temperature during the summer maximum. 

 The thermal range of the habitats of the stenothermal species is not uniform; 

 this is not yet sufficiently understood.** 



The inhabitants of stagnant water bodies in the plains or water bodies 

 with a slow current are usually placed in the group of eurythermal forms 

 (in the broad sense of the term). These water bodies are usually well 

 warmed for long periods and have a relatively high and constant summer 

 temperature with a maximum of 22—25° or more; eurythermal forms avoid 

 cold water with a low average yearly temperature; some species, e. g., 

 Limnophilus n i g r i c e p s, whichhas a wide ecological range (especially 

 a wide thermal range), occur in cold-water lakes (e. g., in Lake Teletskoe) 

 in biotopes in which the water temperature is unusually low in summer 

 (8-12°). In the southern latitudes of the USSR, e. g., in Tadzhikistan, 

 Trichoptera avoid small water bodies, including water bodies in which 

 Anopheles breeds, which may reach a temperature of 30—32° in summer, 

 although the oxygen regime of these open water bodies which are rich in 

 green vegetation would not prevent the occurrence of caddis flies. 



The larvae of Calamoceratidae live in the Far East among algae and 

 detritus in calm backwaters of rivers at a constant high summer temperature 



* According to my observations in the region of Ropsha, Zaborot'ye, Gostilitsy, Taitsy and Pudost' in 1926—1928. 

 ** Ross interprets the concept of cold -adapted forms broadly, including in this category whole families of the 

 Palearctic and Holarctic region (e.g., all Phryganeidae and Limnophilidae). He considers life in cold and 

 cool water as the ancient mode of life of caddis flies, which was characteristic for the whole order during 

 the Mesozoic (Ross, 1956:19-20, diagram 2). 



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