342 



Phylum Arthropoda 



topped with a cover. It rests on a base frame so constructed that the 

 trays are tilted to an angle of 22.5 to the horizontal. The slope thus 

 formed is slightly less than the "angle of flow" of corn when piled in a 

 loose heap. It is sufficient, however, to direct the egress of the moths 

 from the trays, and to provide good ventilation. 



The floor and two sides of each tray should be made of material of 

 sufficient strength so that when the tray is filled the bottom will not 



sag, and when stacked each tray will 

 support the entire weight of the trays 

 above. 



The upper end of each tray should 

 be at least %6 mcn below the top 

 edge of the other three sides, in order 

 to provide exit for the moths. The 

 lower end should be formed of 30- 

 mesh copper screening for ventilation. 

 Across the top of the tray and flush 

 with the rear end is firmly fastened 

 a wooden "stop," 2 inches wide, in 

 order to hold each tray and the top 

 cover in position. The upper ends of 

 the trays should be formed so that 

 when the trays are stacked in place 

 they form a flat, vertical wall. 



In setting up a unit, each tray is 

 filled with corn before adding the next 

 tray. Care should be taken to make 

 the top surface of the corn even with 

 the top edge of the upper end and 

 parallel with the bottom of the tray 

 above, thus leaving a space of % 6 

 inch in height over the entire surface of the corn. 



When the unit is filled and the cover in place, a strongly woven cloth 

 is loosely draped over the vertical front of the stack and fastened on 

 top and at the sides with felt-lined batten placed flush with the front 

 surface. The lower edge is fastened to a flange of the collecting tube 

 extending along the entire front below the bottom tray. 



The tube is made of sheet iron, 1% inches in diameter, with flanges 

 2% inches in width, which diverge outward from a slot % 6 inch wide 

 extending along the top side of the tube for the width of the trays. 

 The tube is held in position by the inner flange, which is inserted 

 between the base and the bottom tray. It is placed so that the inner 

 side of the slot is flush with the upper end of the bottom tray. Attached 



Fig. 66.- — Diagrammatic cross section 

 through the center of the "tilted bin" 

 type of production unit. 



