BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 69 
eliminates a serious source of valve failure and leakage. This valve 
is now in commercial production and has been adopted by the Armed 
Forces. 
New Filtering Units for Respirators Developed 
With the cooperation of the manufacturers of protective safety 
equipment, new filtering units for use on respirators were developed. 
These are effective against mists, dusts, and low-vapor concentrations 
of TEPP. They are now in commercial production. Units pre- 
viously found to give satisfactory protection from parathion and 
nicotine were found also to be effective against EPX, dieldrin, aldrin^ 
and chlordane. 
Methods of Dispersing Lindane Vapors Compared 
The relative efficiency of various methods of dispersing lindane 
vapors for insect control was investigated. Animal shelter units were 
used in these experiments. The methods included use of a carbon 
dioxide-propelled lindane solution, application of residual water-dis- 
persible lindane spray to walls, a thermal lindane vaporizer, and 
the blowing of air through lindane-treated filter screens. The max- 
imum lindane concentration found was 17 micrograms in 1,000 cubic - 
feet, regardless of the method of application. The residual spray 
gave good house fly control until the deposit became covered with dust. 
To maintain effectiveness, walls and ceilings should be sprayed at 2- to 
3-week intervals. Lindane-treated filter screens should be protected 
by air filters to prevent accumulation of dust. Carbon dioxide-pro- 
pelled lindane solution applied weekly was efficient. The efficiency 
of the vaporizer declines noticeably after about 15 days of operation. 
Analyses Made of Peanuts Following Cotton Treated With 
Benzene Hexaehloride 
A colorimetric method for determination of minute amounts of 
benzene hexaehloride has been developed and satisfactorily adapted 
to the analysis of soils and peanuts. This method was used in deter- 
mining the possible occurrence of this insecticide in peanuts grown 
in soil previously planted to cotton that had been treated with benzene 
hexaehloride to control insects. The work was done in cooperation 
with the Bureau of Plant Industry, Soils and Agricultural Engineer- 
ing and the Bureau of Human Nutrition and Home Economics. As 
little as 5 micrograms of benzene hexaehloride can be determined. 
Samples of peanuts and soils were collected from fields previously 
planted with benzene hexachloride-treated cotton. Thirty-nine soil 
samples and 65 peanut samples were analyzed. The peanut samples 
included those from fields that had received 50 pounds or more of 
dust containing about 25 percent total benzene hexaehloride an acre. 
In no case was any significant amount of benzene hexaehloride found in 
the samples. 
Isolation of Essential Ingredient in Gypsy Moth Lure Attempted 
Studies were continued on the isolation and chemical identification 
°f gyptol? the attractant material secreted by the female gypsy moth. 
This lure has been used widely in trap-surveys for this insect. On 
