intersection; the 3rd thread is drawn almost parallel to the 1st and is glued 

 near the base, next to the 2nd thread; the 4th, 5th and following threads are 

 drawn in the same manner; this results in a net of oblong quadrangular 

 meshes, with a median zigzag line dividing the net into a right and left half 

 with almost parallel threads in two directions (Figure 12 6); Sattler 

 (1958:157) states that published drawings showing the net with regular 

 quadrangular cells in one direction are wrong. The frame is not always 

 almost circular in nature; its cells are not so regular, and the intervals 

 between the threads attached to the frame increase from bottom to top, so 

 that the threads are not parallel. 



Drawing a free part of thread and fastening it to the intersection with 

 the threads drawn before requires two types of activity (Figure 127); in the 

 first type the larva is extended, the head is directed forward, the mid- and 

 hind legs are widely separated and the forelegs are extended along the 

 ventral margin of the head; in the second type (made more complicated by 

 interruptions for attaching the threads), the body of the larva is curved, the 

 head is inclined downward and the mid- and hind legs are held close to the 

 body; the distance between the stretched thread and the next thread becomes 

 smaller (see Figure 126). 





FIGURE 129. Capturing net of the larva of Hyd ro psyche angustipennis 

 (after Sattler) 



86 When the current is slow, the net is perpendicular to the current; when 

 the current is rapid, the net is placed at an angle to the current; in an 

 experimental vessel, at a current of 0.1—0.15 m/ sec the nets were built 

 perpendicular to the current; Sattler confirmed the rule of Wesenberg-Lund* 

 in a brook with a more rapid current; he found 23 nets situated at an angle to 

 the current. 



The net is built rapidly; a full-grown larva completes the net without 

 disturbance in 7—8 minutes.' If the net is torn during the weaving, the larva 

 does not repair it but begins to build a new net which is usually less perfect 



A rule on the oblique position of nets in the current (Wesenberg-Lund, 1911a :34; 1943:204—205). 



78 



