areas — toward increasing our insect pests rests upon the bio- 

 logical law that the increase of any animal is limited by its 

 food-supply. Under the natural conditions existing on this con- 

 tinent before the advent of the white man, those insects which 

 fed on wild plants had, as a rule, only a limited food-supply. 

 The apple maggot, or railroad worm, for example, is supposed 

 to have bred originally in the wild haws of the woods. The 

 parent flies had then usually to find here and there an isolated 

 tree bearing the fruit in which it deposited its eggs. Its 

 chances of being caught by a bird or entrapped in a spider's 

 web while on this search were very good, so that the scarcity of 

 the food-supply not only directly limited the number of individ- 

 uals that could be produced, but by being scattered it increased 

 the chances of the adult insects falling a prey to enemies. But 

 in a modern apple orchard all this is changed : the food-supply 

 is almost unlimited, and is so massed together that the insect 

 runs little risk in passing from fruit to fruit, or from tree to tree. 

 Hence it can multiply indefinitely, unless there is some means 

 of checking it. The same line of reasoning applies to a large 

 proportion of our injurious insects. 



We are indebted to our commerce on sea and land for many 

 of the most noxious insects. Brought to our shores from Europe, 

 Asia, or Australia by ships, many of these pests have found a 

 land which for them was flowing with milk and honey, and in 

 which their hereditary enemies had not yet gained a foothold. 

 Consequently they have multiplied without let or hindrance ; 

 and by natural and artificial means— notably the railroad trains 

 — they have rapidly overrun the country of their adoption. 



The abandoned or neglected fields and orchards all over the 

 United States have proven a prolific breeding ground for many 

 insect pests. Too often the efforts of painstaking farmers have 

 been rendered unavailing by the proximity of such sources of 

 infection. An orchard that has outlived its usefulness had bet- 

 ter be converted into firewood than left to die uncared for. 



The destruction of forests has compelled certain insects to 

 resort to cultivated crops for subsistence ; and in some cases a 

 decided change in feeding habits has resulted. So, also, the 

 bringing of the prairies into cultivation has caused many insects 



