December, ’24] 
YAGHi: RONTGEN RAYS AND INSECTS 
663 
the tube as in medical diagnostics to detect boring insects in their food 
substances and got successful results with the following species of larvae: 
Apriona rugicollis Chev. in mulberry tree, Batocera lineolata Chev. in 
chestnut tree, Melanauster chinensis Forst. in apple tree, Sciapteron 
regale Butl. in grape tree, Pyralis farinalis L. in bean grain, Tinea pel- 
lion ella L. in wool, Calandra oryzae L. in rice grain, Chilo simplex Butl. 
in rice straw and Ptinus fur L. in blankets. Under laboratory conditions 
tests on woody plants made with a coolidge tube permitting a medium 
high energy input in voltage 84000, amperage 4.3 m. a. and hardness 
6.3° , or a less intense ray on rice straw and wool. I suggest the rontgen 
tube may be a very useful apparatus for studying the life of boring or 
parasitic insects. 
Ethyl Acetate—Carbon Tetrachloride Mixture. On April 7, 1922, the General 
Managers’ Association of Chicago (representing the leading railway systems in the 
United States) prohibited, because of the fire hazard involved, the use of carbon 
disulphid and a mixture of carbon disulphid and carbon tetrachloride for fumigating 
railway cars except at points at New Orleans and Baltimore. As a result of a resolu¬ 
tion adopted at the same time and presented to the Secretary of Agriculture, an agree¬ 
ment was drawn July 17, 1922, by the Bureaus of Chemistry and Entomology which 
has resulted in a study of the toxicity of over one hundred organic compounds and 
various combinations of these upon Sitophilus oryza and Tribolium confusum. A 
technical bulletin, “Fumigation Against Grain Weevils with Various Volatile Organic 
Compounds,” has been prepared by the Bureaus giving the results of the work from 
July, 1922, to the spring of 1924. This work and that of the summer of 1924 indi¬ 
cates that a mixture of four volumes of ethyl acetate and six volumes of carbon tetra¬ 
chloride gives an effective non-inflammable and non-explosive fumigant against 
adult weevils in wheat in grain cars. These two fumigants must be tested for freedom 
from odoriferous constituents of low volatility or undesirable odors will be retained 
by the wheat, flour, and the finished loaf of bread. The ethyl acetate should be at 
least 99 per cent pure. Since the vapor pressure of ethyl acetate and carbon tetra¬ 
chloride is almost the same, a mixture of the two vaporizes practically as if it were a 
single compound. 
At present forty pounds of the mixture is recommended for each thousand cubic 
feet of space. The mixture can be had at about ten cents per pound. Since the 
average capacity of a box car is 2,750 cubic feet and contains on an average about 
1,300 bushels of wheat, the cost of fumigating amounts to about 85 cents per 100 
bushels. At present the average discount of weevily wheat is about 2 cents per 
bushel. This charge is prorated as follows: pi cent for fumigation with carbon di¬ 
sulphid, 1/8 cent for blowing and screening, 1-3/8 cents for dockage. Since the ethyl 
acetate-carbon tetrachloride mixture costs about 1 cent per bushel, the new fumigant 
will add to the cost of fumigation, but the extra cost will be offset by the freedom from 
fire hazard. 
Further work must be done outside of grain car fumigation to determine the place 
this fumigant will take in practical control work. 
E. A. Back and R. T. Cotton, Stored Product Insect Investigations, 
Bureau of Entomology 
