Larva of Diptera in Wounds. Fly Blow. 63 



For the horn fly which breeds in the manure of cattle the drop- 

 pings in the fields may be turned over or treated with the agents 

 just referred to. 



Remove Shelter of the Diptera. In all cases the removal 

 from pastures of rank branching weeds, and above all of low dense 

 brush is a valuable measure, in doing away with the shelter which 

 the flies naturally seek and from which they emerge to attack an- 

 imals as they approach. Tall spreading trees with bare stems are 

 less objectionable as the flies prefer to keep near the ground where 

 they are on a level with their victims. 



Exclusion of Flies from Buildings. By keeping the inte- 

 rior of the building perfectly dark, diptera which fly in the day- 

 light are driven out. This, however, excludes the purifying 

 agent, air and light. Fly screens over windows, doors, and other 

 openings may be made so secure as to exclude the pests, and in 

 the case of the anopheles this is now proved successful and pro- 

 tective against ague. Yet they seriously interfere with the free 

 circulation of air. Spence says that in Italy the light is admitted 

 on one side only of a building, and the windows covered with a 

 screen or net with wide meshes through which the flies could 

 easily pass. This imperfect obstruction and the dark background 

 combine in deterring flies from entering and in tempting out those 

 that have already gained admission. If light is admitted on the 

 opposite side of the building the flies continue to enter freely. 

 An analogous resort, which would not interfere with the circula- 

 tion of air, would be to admit fresh air below through tubes so 

 bent that the light of the interior would not be seen and they 

 would appear as dark passages ; then have the outlets in the ridge 

 or under the eaves, similarly bent, and covered at their inner 

 opening by a detached screen which would exclude from the ven- 

 tilating outlet any light coming from the interior of the building. 



The same principle can be availed of to kill the flies carried on 

 animals and prevent them from entering buildings with stock. A 

 small building is made capable of holding one animal, without 

 window and with double doors at each end, closed by springs so 

 as to keep the interior perfectly dark, and having an opening in 

 the ridge leading into a close box having glass on four sides. 

 Each animal is passed through this and the flies, swept off by a 

 brush or broom, at once ascend to the light in the small glazed 



