Flytraps and Their Operation. 9 



the trap and extending downward along the legs about two-thirds 

 of their length. These strips hold the wire in place and give 

 rigidity to the trap, and they are thick enough to project beyond the 

 inner surface of the hoop and form a support upon which the edges 

 of the screen top rest. 



Conical traps with steel frames are satisfactory, but they are less 

 easily rescreened. These, of course, can be constructed only by shops 

 witlL considerable equipment. Traps constructed with a wooden disk 

 about the base of the cone, and a similar disk around the top to 

 serve as a frame, or those with a square wooden frame at the bottom 

 and top, with strips up the corners, are fairly satisfactory. It should 

 be bonie in mind that the factor which determines the number of flies 

 caught is the diameter of the base of the cone, if other things are 

 equal. Therefore the space taken up by the wooden framework is 

 largely wasted, and if it is too wide it will have a deterrent effect on 

 the flies which come toward the bait. For this reason it is advisable 

 that the wood around the base of the cone should be as narrow as con- 

 sistent with strength — usually about 3 inches. 



Under no condition should the sides or top of the trap he of solids 

 material., as the elimination of light from the top or sides has been 

 found to decrease the catch from 50 to 75 per cent. 



TENT TRAPS. 



The tent form of trap has been widely advocated in this country, 

 but recent experiments indicate that it is much less efficient than the 

 cone trap, and usually as difficult to construct and almost as expen- 

 sive. The size of these traps may vary considerably, but one con- 

 structed according to the dimensions given in figure 4 will be found 

 most convenient. The height of the tent should be about equal to 

 the width of the base, and the holes {C) along the apex of the tent 

 should be one-half to three-fourths of an inch in diameter and 1 

 inch apart. The box {A) should be provided with hooks to pass 

 tlirough the eyes on the base {B). Small blocks 1 inch thick are 

 nailed beneath the corners of the tent frame to serve as legs. 



GARBAGE-CAN TRAPS. 



As previously mentioned, Prof. Hodge has adapted the cone trap 

 to use on the lids of garbage cans. It is not advisable to use this 

 trap except where garl)age cans are sufficiently Open to admit flies. 

 In such cases a hole may be cut in the lid of the can and one of the 

 small balloon traps which are obt;iinable on the market attached 

 over the hole. To make the trap effective the edges of this lid should 

 extend well down over the top of the can. The lid should be held 

 up slightly so as to allow the flies to pass under, but not high enough 

 to admit direct light. Practically speaking, the garbage forms the 

 bait for this trap, and when inside the can the flies are attracted to 

 the light admitted through the trap. It is really advisable to have the 

 garbage cans fly proof, so as to prevent danger of fly breeding within 



