300 THE MOSQUITOES OF NEW JERSEY 



stream. If the rate of liquid flow is increased and air stream pressure 

 remains the same, the division will be coarser, while if the rate is de- 

 creased the divisions will be finer. Likewise taking the rate of liquid 

 delivery as constant, increase in pressure of the air stream means fine 

 division, while decrease in pressure of the air stream means coarser di- 

 vision. 



Larvicide may be distributed from the ground by small sprayers or 

 by powerful truck sprayers. Employment of the first type means much 

 man labor while use of the latter means a comparatively small amount 

 of more highly trained labor. Larvicides may be distributed from the 

 air by airplanes or autogiros. Here the larvicide is thrown in the slip 

 stream of the propeller. When the delivering machinery is adjusted to 

 give the proper amount of liquid to the slip stream, a very satisfactory 

 atomization takes place. 



In view of the small load an air machine can carry, it is necessary to 

 use as concentrated material as possible. It has been found that eight 

 gallons of oil per acre impregnated with about one ounce twentyfold 

 extract of pyrethrum flowers per gallon of oil gives a killing film on 

 water surfaces. 



Thus far it has not been possible to distribute New Jersey Larvicide 

 from airplanes with uniformly successful results. This seems to be due 

 to a failure to obtain uniform and adequate coverage. 



