348 
Journal of Agricultural Research voi. xxviii, No. 4 
The investigations have shown that fumigation of beans as it is done frequently 
in warehouses, outside of warehouses under canvas covers, and in loaded freight 
cars does not give satisfactory results. Even in fumigators specially constructed, 
within or adjoining the warehouses, the kill is not always complete, and the 
statement is commonly made that fumigation does not kill the eggs or immature 
stages. 
In cases where carbon disulphide was used, the unsatisfactory results are not 
to be wondered at when one considers the statements of scientific workers along 
this line. In 1895 Osborn and Mally (4) 4 said: “For carbon disulphide to be 
effective there must be two or three applications about three or four weeks apart.” 
Pettit ( 6 ), in 1906, said: “Fumigation of the seed, during a warm spell, using 
carbon disulphide in the regular way . . . should kill all the active beetles, and 
a second treatment, after a period of warm weather, should complete the work, 
if indeed the first does not suffice.” 
Krall, in 1914 (£), questioned the possibility of killing all immature forms with 
one application. Metcalf (5), in 1916, when reporting work done in 1912 with 
Bruchus chinensis L. and B. quadrimaculatus, says that he fumigated them with 
carbon disulphide, “using 4 pounds to 1,000 cubic feet of air space in a very tight 
bin at 74° for 72 hours. Contrary to our expectation, however,, the cowpea 
weevils continued to breed in undiminished numbers, although a great many 
adults were killed at the time the fumigation was done.” 
Wade (7), in 1919, says: “One of the first difficulties encountered in our tests 
was to kill all stages of the weevil in cowpeas by fumigating with carbon disul¬ 
phide for the usual length of time. It was determined before proceeding far that 
all of the immature stages were not overcome by the fumigant, especially where 
several bushels were treated.” 
In view of the foregoing the writer underook to determine which stage of the 
weevils, B. obtectus and B. quadrimaculatus , was the most resistant and which 
stage was least resistant to fumigation with carbon disulphide or hydrocyanic- 
acid gas. 
EFFECT OF FUMIGATION UPON THE EMERGED ADULT 
Table I shows that 2 pounds of carbon disulphide per 1,000 cubic feet at a 
temperature of 53° to 61° F. killed all emerged adult bean weevils, Bruchus 
obtectusy with an exposure of 24 hours. Three pounds of carbon disulphide per 
1,000 cubic feet at 62° to 68° F. killed all emerged adults in 21 hours. One and 
one-half pounds of carbon disulphide per 1,000 cubic feet at 52° to 68° F, killed 
all adults in 48 hours. 
* Reference is made by number (italic) to “Literature cited," p. 356. 
