The distribution of caddis fly larvae in the depth of water bodies is 

 limited because of their high oxyphily. They are restricted to depths of 

 a few centimeters; some species even occur outside the water, in puddles 

 among detritus, especially among fallen leaves at the edge of springs, where 

 rocks are washed by water, or among moss, e.g., the larvae of Stactobia 

 catoniella, Ptilocolepus granulatus, Tinodes assimilis, 

 Crunoecia irrorata, Berea maurus, B. pullata, Ernodes 

 articularis, which belong to the fauna of humid biotopes called "fauna 

 hygropetrica. "* 



In rivers with an almost uniform distribution of oxygen in the water, caddis 

 flies (mainly Hydropsychidae) are common near the banks along the whole 

 profile of the river; they have been found in the Volga to a depth of 10—11 m 

 and in the Amur to a depth of 17— 20 m. In lakes, larvae of Trichoptera 

 occur mainly in the littoral, where a high oxygen content is created in 

 summer by the dynamics of the water and photosynthesis. In oligotrophic 

 lakes with a high oxygen content and in deeper water layers, caddis flies 

 also occur in the sublittoral; a few specimens also in the upper profundal 

 zone. 



In the lakes in Karelia, species of Molanna (M. angustata, M. pa 1 - 

 pata, M. s ubm a r g in a 1 i s), Mystacides a z u r e a, Oecetis 

 ochracea, Cyrnus flavidus occur in the sublittoral; there are also 

 isolated specimens of Apatania wallengreni, Chaetopteryx 

 sahlbergi and Phryganea striata; some of the above species also 

 occur in the upper profundal zone to a depth of 10— 20 m (Lepneva, 1928:98— 99; 

 Gerd, 1949:85, 178). In the littoral of Lake Teletskoe Mystacides 

 d e n t a t a and Apatania stigmatella may be found to a depth of 

 20-30 m (Lepneva, 1949:169, 181, 189). The species of Apataninnae are 

 richly represented in the littoral of Lake Baikal; they are common at a depth of 

 106 25— 30 m; they have been recorded rarely from the profundal zone, to a 

 depth of about 200 m (Bebutova, 1941:82-84; Levanidova, 1946). 



Temperature 



The larvae of Trichoptera commonly inhabit continental waters; they 

 are therefore adapted to very different thermic regimes. In high and middle 

 latitudes of the USSR, all caddis flies in temperate and cold climates tolerate 

 a low water temperature in winter (near 0°) and some species even become 

 frozen in the ice. In rivers with bottom ice, there is often the whole 

 hibernating fauna of caddis flies enclosed in the ice; in the Neva, for 

 example, viable larvae of Hy d r o p sy c h e nevae and Arctopsyche 

 ladogensis are found in pieces of bottom ice. It is therefore interesting 

 to discuss the relation of Trichoptera in temperate latitudes to the upper 

 limit of the thermic range, i.e., to the maximum water temperature in summer. 

 Caddis flies, which live in insolated shallow water, do not include steno- 

 thermal species (eustenothermal species) and resemble species living in the 

 depths of lakes or relict species in caves; the latter species live at a 

 constantly low temperature with small yearly fluctuations. We usually 

 consider as cold-water stenothermal species in the broader sense the 



* For further details on the Trichoptera of the "fauna hydropetrica" see: Thienemann, 1905b: 553-556; 

 1909-1911:66-68; 1923,1924,1925:46-51; Vaillant, 1954, 1956:152-243; Jacquemart, 1960; Danecker, 

 1961. 



97 



