212 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. 



be covered with canvas as shown in figure 22. Two pieces of canvas 

 meeting in the center are tacked on the sides of the opening. Pieces 

 of rubber tubing extending transversely are sewed on the canvas and 

 their ends securely tacked down at the sides, leaving them otherwise 

 free, excepting as they are fastened in the canvas. As the cage is 

 pushed on to the vine the canvas and the free ends of the rubber give 



Fig. 23. A photograph of the interior of the cage shown in Fig. 21, after 

 15 minutes use where hoppers were very abundant. The white specks at 

 the back each represents a hopper, stuck in the oil with which the screen 

 has been smeared. A portion of the tray at the bottom, which is outside 

 the shadow on the left, shows a solid surface of hoppers. 



way, but immediately spring back into position again on account of 

 the flexibility of the rubber tubing. This canvas may be covered with 

 oil, and thus the bottom is completely covered. 



The advantage of the screen is that it does not shut off the light 

 and also allows the wind to blow through so that the great majority of 

 the hoppers will go downward and toward the leeward side of the vine. 

 A cage built of canvas was tried, but proved unsuccessful because 



