22 JAMESTOWN CONGRESS OF HORTICULTURE 



Insects are injurious: 



(1) As destroyers of crops and other valuable plant life. 



(2) As destroyers of stored foods, dwellings, clothes, books, etc. 



(3) As injuring live stock and other useful animals. 



(4) As annoying man. 



(5) As carriers of disease. 

 Insects are beneficial : 



(1) As destroyers of injurious insects. 



(2) As destroyers of noxious plants. 



(3) As pollinizers of plants. 



(4) As scavengers. 



(5) As makers of soil. 



(6) As food (for man and poultry, song birds and food fishes) 

 and as clothing and as used in the arts. 



Thus insects are about equally divided as to their injurious and 

 beneficial characters. Their injuries to farm and forest products and 

 their role in the transmission of diseases in man and live stock doubt- 

 less include the principal losses which they occasion. Notwithstanding 

 the enormous destruction of useful products caused each year by 

 insects their injuries are largely offset by the assistance which the 

 beneficial forms render in the destruction of noxious species and in 

 the pollination of plants. The beneficial influence of insects in these 

 ways is but little understood by the public in general. It is perhaps 

 not too mu h to say that our very existence depends on these friendly 

 insects which insure our crops by effecting the fertilization of plants 

 and keeping down injurious species. 



In nature, insect and plant species have gradually evolved together, 

 and there has come about a very complex though well balanced rela- 

 tionship between the plants and insects, and between the insects them- 

 selves. The destruction of the native plants of the prairie and forest 

 and the planting of cultivated plants has quite changed the natural 

 conditions surrounding our native insects, and they have been forced, 

 or from preference have attacked the succulent cultivated crops and by 

 reason of its great abundance individuals of a species are able to de- 

 velop in enormous numbers. While we have numerous native species 

 of first-class importance, as the peach borer, potato beetle, etc., the 

 considerable majority of our worst insect pests have come to us, at 

 various times, from other countries. In practically all instances, these 

 introductions have here become more destructive than in their native 

 homes, for reasons not always explainable, but in numerous instances 

 from the fact that their insect enemies which at home serve to keep 

 them reduced have not been brought over with them. The idea was 

 early suggested that the native country of a given imported species be 

 determined, and its natural enemies be introduced to prey upon it. 

 It is a pleasing proposition to thus array the forces of nature against 

 each other, but that it should uniformly be successful involves a good 

 deal more than is at first apparent. 



Important as are these, and other natural agencies, as rains, wind- 

 storms, forest fires, heat and drouth, in the destruction of noxious in- 



