Flytraps and Their Operation 5 



inches on the arc C />, starting at (', as there are inches around the 

 base of the cone, which in this case is about 56i/^ inches, reaching 

 nearly to the point E. Then add one-half inch for the lapping of 

 the edges of the cone, and one-half inch which is taken up when the 

 cone is tacked in, thus making a total distance from 6' to i^" of 57^/^ 

 inches. Draw a line from A to C and another from A to E, and cut 

 out the pattern on these lines and on the arc from C to E^ as shown 

 in Figure 3. The edges AC and AE are then brought together, 

 lapped one-half inch, and sewed with wire or soldered. After the 

 aperture of the cone is formed by cutting off the apex, as previously 

 described, it is ready for insertion in the trap. 



In order to figure the distance around the base of a cone of any 

 given diameter multiply the diameter by 3.1416 or 3^. 



Fig. 3. — Method of laying out a pattern for the construction of a cone. Cut out on 

 cui-ved line from to E and on dotted lines from A to and A to E 



The height of the legs of the trap, the height of the cone, and the 

 size of the aperture in the top of the cone, each is of importance in 

 securing the greatest efficiency. 



OTHER FORMS OF CONICAL TRAPS 



A modification of the previously described trap has been made by 

 D. C. Parman of the Bureau of Entomology. The principal point 

 of advantage in this type is that it can be made more quickly and 

 with fewer tools. The principles and dimensions are the same, the 

 most striking difference being the absence of a wooden top. A 

 single hoop with the thick edge down forms the upper frame 

 of the cylinder and the entire top is made of screen. A circular 

 piece of screen with a diameter about 3 inches greater than the dia- 

 meter of the cylinder is cut; a hoop with a diameter equal to the 

 inside of the top of the trap is then made of heavy wnre and laid 

 upon the disk of screen and the edges of the screen bent in over it. 



