The current is made by an air jet; this is convenient as the current has 

 a definite direction; it is weaker in some places so that there are parts 

 with a current of varying speed; this enables the insects to select places 

 with a favorable current. Sattler (ibid.) made his observations on the 

 larvae of Hydropsyche in such aquaria (Figure 179). 



FIGURE 178. A breeding cage in a brook 



7> /% 



FIGURES 179-180. Flowing-water breeding cages: 



179 — aquarium of Sattler; the small circles represent air bubbles; the arrows indicate the 

 direction of the current; k — stones; 180 — serial breeding cages of Wiggins (after Wiggins). 



A convenient device for breeding rheophilic caddis fly larvae is the 

 running-water tray of Frantsev. His description is as follows: "The model 

 l ^ 4 consists of 2 parallel oval trays, 3 m long. The trays are made of vinyl; 



172 



