INSECTS AFFECTING MAN AND ANIMALS 183 



Prof. C. F. Hodge (see 40c). They should be placed in 

 windows on the brightest side of the barn and near to the 

 cows or horses within. Other windows should be darkened 

 by hanging canvas or sacks over them, so as not to interfere 

 with ventilation, but so as to drive the flies to the lighter 

 window. Fig. 130 shows the construction of the trap. At 

 the bottom a space about one-fourth of an inch wide, running 

 entirely across the window, is left on both sides of the frame. 

 Above this is placed a roof or ridge of screen wire having 

 holes large enough for the flies to pass through punched 

 through its top at two-inch intervals. To capture the house 

 flies suitable bait is placed in the pans beneath this ridge. 

 The flies ascend through the holes and are then unable to 

 escape. The sides of the trap are also made of wire screen- 

 ing bent inward and upward in two horizontal folds across 

 the window, one toward the bottom and one toward the top. 

 The ends of the screen are tacked tight and a series of small 

 holes are punched along the inner edge of each of the folds. 

 The angles of these folds should not be too sharp and less 

 than 45 or the flies will not go up the angle. In trying to 

 go in and out of the window the flies enter the holes at the 

 apex of the fold, but are then unable to escape , as on the in- 

 side the holes are on the projecting ridge and are not found 

 by the flies, which seek the light. Portable traps made on 

 much the same plan may be used within the stable. 



114. Mosquitoes (28, 34, 38, 46, 57).* Formerly mos- 

 quitoes were regarded merely as aggravating nuisances, but 

 in recent years we have come to learn that certain species 

 are among the most important carriers of disease, so that 

 the whole problem of mosquito control has assumed new 

 interest. The common house mosquito f (46), is entirely 

 innocent of carrying disease, so far as we know, but about 

 * Family Culicidae, see page 133. f Culex pipiens. 



