(Figures 44 and 114, A). The spinning apparatus is divided into a secretory 

 and an excretory part (Figure 45); both tubes join in the head, forming a 

 common duct which opens at the tip of the labium; the spinning glands of the 

 larva are therefore also called labial glands. Near the boundary of the 

 secretory part, the duct forms an organ which produces the filament 

 (Figure 46), and is called the silk press (Gilson, 1894). 



40 



03 



40 



FIGURES 40 and 41. Tracheae of thorax and abdomen (after Novak): 



40 - system of the left lateral trunk of the larva of Plectrocnemia 

 conspersa; 41 - right and left lateral trunks and tracheal system of the 

 intestine of Hydropsyche angustipennis. 



1 - dorsal cephalic trachea, 2 - ventral cephalic trachea, 3 - left lateral 

 tracheal shaft, 4 - tracheae of anal legs. 



36 



