14 



CIRCULAR 457, U. S. DEPT. OF AGRICULTURE 



TKAPS 



Traps are of many varieties, but they all depend upon light to 

 attract the flies to them. They have been used with success, but they 

 should be considered merely supplementary and not be depended 

 upon to the exclusion of dusting. The simplest type of trap is a 

 pane of glass set into the south or east end of the house, usually in 

 the door, about a foot or more above the floor. Fly paper or sticky 

 tree-banding material is placed about this to catch the flies as they 

 come to the light, or a pan containing a little kerosene may be placed 



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Figure 4. — Eggs of mushroom fly, Sciara ijauciseta, X 16. 



beneath it, into which the flies will fall and be killed. The pane of 

 glass should not be too large, as the ends of the beds will then be 

 too well illuminated and the female flies will often oviposit before 

 they go to the glass, or they will not be attracted to the glass at alL 



Experiments have shown that a glass pane of 72 square inches or 

 less is most satisfactory for attracting flies to daylight. 



Another type of trap is one in which the flies are attracted by an 

 electric light, drawn in by a fan, and retained in a bag or jar. 

 A trap of this type, used experimentally in a very heavily infested 

 house, caught over 187,000 flies in one 24-hour period, of which 75 

 percent were females, and more than half of these had not laid all 

 their eggs. As in the case of traps depending upon daylight to 

 attract the flies, the illumination should not be too intense. A 40- 

 watt white-frosted electric -light bulb has given most satisfactory 

 results. If either the daylight or the artificial light used as a lure is 

 not intense enough the flies will not be attracted in great numbers, 

 and if it is too intense they seem to be satisfied before they actually 

 reach the trap and do not come any nearer to it. 



