INSECT ENEMIES — PACKARD 335 



and consumption. During the first World War and during the present 

 one special efforts have been made to find ways and means of meeting 

 the situation. 



Of several hundred species of insects found associated with stored 

 grains or grain products some 50 or more kinds of moths, weevils, and 

 beetles are seriously injurious when conditions are favorable to their 

 activity. The larvae of some species bore into and mature inside of 

 (he kernels, while both the larvae and adults of others are free-living 

 among the kernels or in milled cereal or flour (pi. 19). The larvae of 

 some of the moths not only eat the^e products but s])in silk as they move 

 about, sometimes forming a thick webbing on the surface or within the 

 outer layer. High temperatures and ample moisture are favorable to 

 the development of all these insects. Hence they are a constant source 

 of annoyance and loss in warm-temperate and tropical regions. They 

 are cosmopolitan in distribution, however, and in warm, moist seasons 

 or under suitable conditions such as prevail in flour or cereal mills, 

 they become serious pests in the more northern latitudes as well. When 

 an infestation is once started in stored grain, enough heat and moisture 

 are often generated by the insects themselves to provide for their con- 

 tinued activity and to cause injury to the grain. Some species begin 

 their attack on the grain in the field before it is stored and are carried 

 Avith it into the bins, warehouses, elevators, and mills. Others live 

 and breed chiefly within these storage places. Most of the species are 

 active fliers in the adult beetle or moth stage and spread locally by 

 flight, but the principal means of dispersion is the commercial ship- 

 ment of grains and cereal products. They have been carried all over 

 the world in this way. 



The first essentials for the protection of stored grains and cereal 

 products are good storage facilities and sanitation. Tightly con- 

 structed bins, warehouses, and mills that can readily be kept clean and 

 that will prevent the escape of fumigants when it becomes necessary to 

 use them are basic to satisfactory application of insect-control meas- 

 ures. These insects breed in undisturbed accumulations of grain or 

 floury residues wherever they are allowed to occur, such as in floor 

 cracks, behind lining boards, in supplies of stock or chicken feeds, in 

 used feed or flour sacks, in conveyor machinery, and in household cup- 

 boards. Such accumulations serve as sources from which infestations 

 spread to stored grain, cereals, or flour, and obviously should be 

 eliminated. 



Owing to the more or less frequent or constant introduction of new 

 infestations in one way or another, however, the periodical application 

 of more drastic measures becomes necessary. The most generally use- 

 ful treatment is fumigation. Several different fumigants are in com- 

 mon use and the best one to select depends on the circumstances. The 

 so-called heavier-than-air gases, especially ethylene dichloride or 



