fil \\\r.\L REPORTS 01 DEPARTMENT OF AGRICULTURE, 1952 
similar for both species of livestock, averaging 7s p. p. m. for aldrin, 
72 p. p. in. for dieldrin, and L6 |>. ]). m. tor chlordane. Chlordane 
residues disappeared after •_: months but aldrin and dieldrin were 
found in the i'ai ( .» months after Insecticide feeding ceased. 
There was no evidence of accumulation of methoxychlor in tat of 
beef cattle U'<\ for 30 days on a diet containing l'> p. p. m. of this 
insecticide. This insecticide i- not likely to create a residue problem 
in fat of cattle consuming forage treated with the material. 
INSECTICIDE INVESTIGATIONS 
Rest Methods for Residual-Type Spray Applications Studied 
Performance requirements were established for applying residual 
sprays to obtain the besl deposition and leasl contamination of sur- 
rounding ait-. The percentage of deposit was determined by spraying 
measured quantities of liquid against absorbent paper ana weighing 
the resulting deposit. Particle size was measured by collecting a 
spray -ample on a glass slide and measuring the droplets under a 
microscope. 
When sprays were directed downward practically all spray droplets 
deposited on the paper. Spray- directed horizontally toward a ver- 
tical surface were found to deposit in inverse proportion to the dis- 
tance between nozzle and surface. The deposit reduced gradually 
with distance until about a 75-percent deposit was reached. Beyond 
this the percentage of deposit dropped oil rapidly. The deposit was 
greater when enough spray was released to generate an airstream in 
the direction of the spray. The distance at which 75 percent or more 
of the spray deposited was greater with larger droplets, narrower 
spray angle, or greater output. 
It was concluded that for best deposition the distance between 
nozzle and surf ace must be limited to that which will allow 75 percent 
<»!• more of t he -pray to deposit. For least contamination of surround- 
ing air the mass median diameter of the droplets should be .~»0 microns 
or larger to reduce dri ft to a minimum. 
Ensecticidal Vapors Utilized in Airplane Disinsecti/ation 
A new approach to disinfestation of airplanes was studied during 
the year using Insecticidal vapors. Fiber-glass filters coated with 
lindane are placed in the air intake ducts of pressurized plane cabins. 
Vapors given oil' into the air stream are carried throughout the 
plane cabin and are lethal to insects. The extremely low concentra- 
tion is not considered harmful to humans and is not detectable by 
either crew or passengers. Thorough tests were made in the labor- 
atory before th' 1 method was tried on planes. This method requires 
longer exposure period- than when aerosols are used. Since it is in 
operation all during the time of flight, it shows considerable promise. 
and invest igat ions are cont inuing. 
Nerve Ganglia of House Fly Isolated in Insecticide 
Resistance Studies 
A technique has been developed for isolating the nerve ganglia of 
the house fly, so that direct applications of insecticide can be made. 
When DDT is applied to the ganglia of susceptible and resistant flies, 
