LARVICIDES 297 



"The three general fields of protection are the unscreened porch ; the 

 small yard not exceeding 2,500 square feet, with a limited number of 

 high shrubs or trees ; any area exceeding 2,500 square feet. 



"In the case of the unscreened porch, control methods are simple. 

 The larvicide, diluted 1—14, sprayed over the porch to kill mosquitoes 

 already there, and then directed away from the porch, will set up a pro- 

 tected zone. The application must be repeated as mosquitoes appear in 

 flight, particularly if the porch is not protected by shrubs or other veg- 

 etation from which the larvicide will slowly evaporate, A large hand 

 sprayer or an electric vaporizer is sufficient equipment for the control 

 of small areas. 



"The schedule for yards and larger areas is more complicated. For 

 convenience, it is divided into (1) examination and planning, and (2) 

 the application of larvicides. 



EXAMINATION 



"A thorough survey should be made of the area twenty-four hours 

 before application and the following items observed. When this infor- 

 mation is available, the Director of Operations should prepare a plan 

 which should contain enough detail to enable the spraying crew to com- 

 plete the job without further instruction. 



"1. Size of area. Determine the exact area to be protected. Insist on 

 a free margin of approximately 100 feet wide around the area. 

 Should the sponsoring agency neglect to provide such a margin, 

 do not attempt control. 

 "2. Other conditions to be noted: 



"A. Source of mosquito annoyance and direction of migration. 

 "B. Note extent of mosquito resting places, such as dense shrubs 



or woods. 

 "C. Prevailing winds both before and after dusk. 

 "D. Types of vegetation. Fine lawns, flowering plants, and ten- 

 der shrubs must be noted. 

 "E. Type and location of buildings. 



"F. Nature of activity or program. Types of clothing, effect of 

 noise, time of intermissions, should be noted and spraying 

 plans made accordingly. 

 "G. Time activity is planned to start and stop. 

 "3. Plan of action : 



"A. Locate a central position for spraying equipment and open 

 avenues of movement. 



