THE BROAD-BEAN WEEVIL. 77 
retically correct, i. e., for absolutely air-tight inclosures, there is 
great difficulty in securing such a degree of tightness; hence greater 
strength and longer exposure are desirable. On the other hand the 
rate advised by many is excessive, especially when three days' expo- 
sure is also advised. 
In some cases hydrocyanic-acid gas at the usual rate of 10 ounces 
of cyanid of potash to 1,000 cubic feet will be found useful, where 
for any reason bisulphid of carbon is considered undesirable. This 
remedy has not been tested for this species in its occurrence in broad 
beans, but it has been successfully employed against related weevils 
and it should not be difficult for this gas to penetrate a mass of these 
larger seeds. 
In the practical fumigation of beans, peas, and similar seeds with 
bisulphid of carbon it should be first understood that the more nearly 
air tight the receptacle the more perfect the fumigation. Infested 
seed should be placed in large barrels, which should then be closed 
tightly, or in specially made fumigating boxes, bins, or small houses. 
After filling the receptacles with the seed the bisulphid is poured into 
evaporators, for which purpose tin pie plates are most valuable, 
placed on the top of the seed. The gas, being heavier than air, 
descends through the mass of seed, and, properly applied according 
to directions, will kill all of the insects contained. At the end of about 
48 hours, which is sufficient for perfect fumigation under these condi- 
tions, the seed should be removed and thoroughly aired before being 
packed away for storage. If left in the receptacles, the dead bodies 
are apt to decay, and thus injure the seed for food or planting. 
The usual precautions not to bring fire of any kind, such as a lighted 
cigar, into the vicinity of the place where the operation is being per- 
formed should be observed. Where the covers or doors of the recep- 
tacles do not fit'perfectly tight, paper should be carefully pasted over. 
In any form of leguminous seed the penetrating power of bisul- 
phid of carbon, hydrocyanic-acid gas, and other gases is as nearly 
perfect as could be wished. 
CONSTRUCTION OF A FUMIGATOR. 
The extensive pea growers of our Northern States, especially in 
New York and Michigan, have largely adopted what was known in 
former years as Tracy houses, named after Prof. W. W. Tracy, now 
of this department, and also called "bug houses," for the fumiga- 
tion of peas affected by the related pea weevil. The opinion is some- 
what prevalent that in spite of the fact that we can control the broad- 
bean and pea weevils by means of heating, soaking, and similar 
mechanical methods, everything considered, fumigation on a large 
scale, while a little more expensive, is more thorough and requires 
less labor. The same is true of grain and other material in general 
