186 Forty-first Report on the State Museum. 



in three years, in apricot and aijple trees that had been grafted on other stock. They 

 were of exuberant growth, in healthy foliage and were bearing, abundantly, normally 

 developed fruit. It is described as follows: 



" In the morning the trees appeared to be in full health; shortly after 10 o'clock the 

 leaves suddenly became weak and every leaf, without exception, hung lifeless on the 

 tree. In the afternoon the fruit and bark began to shrink, and in forty-eight hours all 

 the leaves and young shoots were entirely withered and the fruit shrunken and nearly 

 dried up. Two trees were tested with the knife, and it was found that the paralysis 

 and death had taken place from the grafting-point upward." 



Increase of Insect Kavages. 



Passing now to insect pests — it is surely evident to every fruit grower that, with each 

 successive year, the ditYiculty of growing choice and perfect fruit is becoming greater. 

 He can no longer ignore the insect as an insignificant object in nature, almost 

 unworthy of regard. The myriad hosts confront him on every side and demand his 

 attention. They claim the choicest products of his labor — not a tithe of them, which 

 might, perhaps, be granted, but the eotirety. It is a struggle for mastery, in which he 

 must conquer the insect, or the insect will conquer him. 



The primary causes that have necessitated this warfare have been given you in 

 general terms, but the consequences of these might not extend much beyond a multi- 

 plication of the individuals of a species. But beyond this, another serious element is 

 forced upon us, viz., a continual increase in the number of species preying upon fruits. 



Food-habits of Insects. 



You all know that our noxious insects are divisible into many groups, indicated by 



the food-plants upon which they subsist. Thus we have our grass insects, our grain 



insects, insects infesting our forest trees, those infesting our flowering plants, those 



attacking garden vegetables, a long list of household pests, those that live upon our 



domestic animals, etc., etc. Insects are more or less particular in their food. There 



are those that confine themselves to a certain species of plant and will starve rather 



than change to another. Very many will feed upon allied plants as associated by 



structure and character in a genus or a family; while others, polyphagous species, as 



they are termed, extend their range through different and often dissimilar orders of 



the vegetable world. 



Change of Food-plants. 



Thus it is that the fruit grower not unfrequently has to contend with some insect 

 depredator quite new to him and to his locality. He submits it, as he should, to some 

 authority in entomology, and it is found to be a species previously known as subsisting 

 on some other food-plant. Chance, it may be, has brought it to an apple tree, and it at 

 once finds in its material, food more agreeable and attractive to it than that on which 

 it had hitherto fed. It becomes an apple tree insect, and displays iinder the stimu- 

 lating effect of its changed diet, far more destructive habits than those that before 

 pertained to it. To illustrate: A little bark-boring beetle (Scolytus rugulosus), which. 

 for several years had been known to us only as destroying cherry, peach, and plum 

 trees, has been discovered by me the present year as working in large numbers 

 beneath the bark of apple trees and quickly killing them by running its galleries over 

 and around the trunk until it is completely girdled. 



Introduction from Abroad. 

 Again, the new pest proves to be an introduced species, brought over from Europe 

 through some commercial avenue, readily planting itself in its new home, and spread- 

 ing from thence over the country as broadly as the area of its food-plant or suitable 

 climatal conditions will permit. And almost without exception, a .species thus intro- 

 duced from abroad, unattended by its natural parasites and freed from other enemies 

 that had learned to prey upon and control it, is at once transformed into a pest of such 

 magnitude, that its harmlessness in the old world is in marked contrast with its ravages 

 in the new. 



