The high oxyphily of the larvae is proved by the fact that they occur 

 only in parts of water bodies with a high oxygen content. One of the optimal 

 habitats which contains a large and diverse fauna of caddis flies is 

 mountain brooks and streams with cold and oxygen- saturated water. The 

 most favorable biotopes of caddis fly larvae in lakes are in the littoral zone; 

 in the surf zone a high oxygen content is ensured by the dynamics of the 

 water, and in plant thickets by photosynthesis. The assimilation of green 

 54 plants often results in a surplus of oxygen on clear sunny days and in the 

 release of oxygen in form of gas bubbles. 



FIGURE 80. Phryganea stria t a: egg masses (A) and lst-stage larva (B) 

 (after Siltala) 



The oxygen consumption was experimentally determined and calculated 

 for 1 g of live weight of the larvae (Kolenkina, 1951:55); it varies strongly 

 in different conditions and in various species of caddis flies. In mobile 

 larvae of Phryganeidae, for example in almost mature larvae of Oli- 

 gostomis reticulata the oxygen consumption is 4.22 mg/hour at a 



49 



