2 BULLETIN" 1313, U. S. DEPARTMENT OF AGRICULTURE 



and the Baltimore & Ohio at Locust Point, Md., when cars are isolated and 

 protected, until some other satisfactory suitable substance can be provided, and 

 further, that each carrier, member of this association, shall issue, without delay, 

 necessary instructions prohibiting its use. 



The following resolution was also adopted at the same time by this 

 association: 



That because of the presence of bran bug and weevil in grain and the great 

 danger being done thereby, the chairman of this association communicate with 

 the Bureau of Agriculture, Washington, D. C, advising of the action taken by 

 this association and recommending that such investigations as may be necessary 

 be made by the Government to produce a substance for this purpose which can be 

 used with safety. 



The investigation reported in this bulletin was undertaken because 

 of the action taken by these railroad officials. 



Carbon tetrachloride, hydrocyanic acid gas, sulphur dioxide, 

 chloropicrin, naphthalene, phosgene, arsine, cyanogen chloride, and 

 many other substances have been tested as fumigants for grain 

 weevils by various investigators, who have reached the following 

 conclusions: Carbon tetrachloride is ineffective under practical 

 conditions; hydrocyanic acid gas fails to kill weevils very far below 

 the surface of the grain; sulphur dioxide has low toxicity, injures 

 ironwork, destroys the germinating power of wheat, makes a sticky 

 dough (4), and retards fermentation, the bread obtained being heavy 

 and unfit for consumption ; carbon dioxide is effective only in tightly 

 sealed containers .and at relatively high concentrations; chloropicrin 

 shows promise of being a practical fumigant, but is not yet com- 

 mercially available; naphthalene is not very effective and has an 

 objectionable odor; phosgene is poisonous to man, comparatively 

 nonpoisonous to insects, and, because of its high vapor pressure, 

 difficult to control; the toxicity of arsine to insects is comparatively 

 low; the effect of cyanogen chloride as an insecticide is practically 

 the same as that of hydrocyanic acid. 



It is evident, therefore, that there is great need for a fumigant 

 which will be effective against injurious insects in wheat and other 

 cereals and also noninnamm able and nonexplosive and neither 

 dangerous nor highly disagreeable to those who handle it. The 

 object of the investigation here reported was to discover such a 

 fumigant, which could be used in place of carbon disulphide. In 

 connection with this investigation, much information on the relation 

 of the chemical constitution of compounds to their toxicological 

 action on insects was acquired. 



EXPERIMENTAL PROCEDURE 



The rice weevil (Sitophilus oryza L.), the flour weevil (Tribolium 

 confusum Fab.) , and the granary weevil (Sitophilus granarius L.) were 

 used in most of the tests, and the Indian meal moth (Plodia inter- 

 punctella Hbn.) was used in a great many. Adult insects of the 

 weevils and the larvae of the Indian meal moth were used. 



The first series of experiments (Tables 1 and 2) were conducted 

 in the apparatus described by Neifert (18). Four-liter glass jars, 

 containing 10 to 20 live weevils of each species tested, were filled 

 with a mixture of air of 40 per cent relative humidity and the vapor 

 of the compound to be tested. After standing for 24 hours at room 

 temperature (21° to 32° C), the percentage of dead weevils was 

 determined. (All specimens were examined after 24 hours, and 

 also after 48 hours, to avoid reporting as dead those which might 



