234 SCHOOL ENTOMOLOGY 



at some distance from other buildings. It should be con- 

 structed of matched flooring so as to be as near insect-tight 

 as possible. The doors should fit tightly, closing on a rabbet, 

 which may be covered with felt or packing. The windows 

 should be covered with fine wire screening to prevent the 

 passage of insects. The floors, walls and ceiling should be 

 made smooth, with no cracks in which insects may hide. It 

 is important that the building be dry, well ventilated and as 

 cool as possible, as reproduction is much more rapid in a 

 warm place, and infested grain will heat more quickly. It is 

 desirable to store grain in bulk, as a smaller surface is thus 

 exposed to infestation, and the moths do not penetrate far 

 beneath the surface. The best means of destroying insects 

 in the small granary is by fumigating with carbon bisulphide 

 (page 335). The room or bin in which it is to be used should 

 be made tight. Bins may be covered with blankets. The 

 liquid may be poured directly on the grain, which it will 

 not injure. Care should always be exercised that no fire 

 comes near the place fumigated, as the gas is exceedingly 

 inflammable. Mills and storehouses which are badly in- 

 fested are often fumigated with hydrocyanic acid gas (page 

 336). Prof. R. I. Smith has shown that sulphur dioxid, pro- 

 duced by burning sulphur slightly dampened with alcohol, 

 will kill most grain insects, but injures the germinating power 

 of the grain. "It was found that the fumes produced by 

 burning 2j pounds of sulphur either in moist or dry atmos- 

 phere of 1000 cubic feet space, for twenty hours, would kill 

 all exposed adult insects and practically all the young stages 

 in the grain, but that this also destroyed its germinating 

 power. . . . While this treatment cannot be recommended 

 for general fumigation, there is no doubt of its being the 

 easiest and cheapest method of fumigating corn cribs, grana- 

 ries and similar places whenever they are being cleaned out 



