50 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 3 



rugineum and Tenedrioides mauritanicus. In tlie course of observa- 

 tions upon the rice weevil, records are kept relating to each of these 

 other species. It appears that any treatment which insured the de- 

 struction of all emerged adults of the rice weevil, was very likely also 

 to destroy the unemerged stages, with the possible exception of the egg, 

 which we have not found in sufficient abundance to enable us to test 

 its resistance satisfactorily. The experiments made thus far indicate 

 that there is a wide working margin between the treatment necessary 

 to destroy infesting insects and that which mil endanger the vitality 

 of the infested seed. It is now certain that no single dosage can be 

 safely recommended for all conditions and subjects in this grain fumi- 

 gation work. The percentage of moisture content in seeds is impor- 

 tant as affecting their degree of resistance to the gas. It is also certain 

 that the temperature prevailing at the time treatment is made has a 

 great deal to do with the effectiveness of a given dosage. Thus, a 

 dosage which will kill all stages of the rice weevil at 67 to 70 degrees 

 F. is not likely to kill more than 60 or 70 per cent at 60 to 65 degrees 

 F. The influence of temperature must certainly be considered as two- 

 fold. First, upon the evaporation of the liquid and the diffusion of 

 the gas, and, secondly, upon the condition of activity or inactivity of 

 the treated insects. It appears that with the high temperatures, when 

 the weevils are most active, a far smaller dose of the insecticide is 

 needed to destroy them and the killing time is really much shorter 

 than when the temperature is below 65 degrees. It seems quite prob- 

 able that this effect of temperature may partly explain the widely 

 varying results which have been reported in the use of carbon 

 di-sulfid. 



According to the chemists, the specific gravity of carbon di-sulfid 

 liquid is 1.29, while the vapor is 2.63 times as heavy as air. One vol- 

 ume of the liquid is said to yield 375 volumes of the vapor. Seventy- 

 seven and six-tenths pounds of the liquid is required to saturate 1,000 

 cubic feet of air at the temperature of 68 degrees, and 84.4 pounds at a 

 temperature of 72 degrees. It is evident, therefore, that in the usual 

 application but a small fraction of the saturated atmosphere has been 

 used. 



In our experimental work, we began with small scale tests, using 

 glass bell jars of two litres capacity, in which the proportion of gas 

 could be controlled and its loss by diffusion entirely prevented. A 

 satisfactory method of obtaining any desired dilution of the gas is as 

 follows : Through a stopper in the bell jar or bottle, two tubes may 

 be passed, both of which should be tightly closable from the outside in 

 some way. One tube should reach to the bottom of the jar, while the 



