16 



CIRCULAR 45 7, U. S. DEPARTMENT OF AGRICULTURE 



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 



/~s 



A 



Figure 5. — Light-suction fly trap: A, frame showing position of fan 



trap assembled. 



B. 



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 on 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 



