240 ILLINOIS STATE HORTICULTURAL SOCIETY. 



inferior animals. If some amongst "them constitute an excellent part- of 

 the food of man, furnish him with eggs, with useful feathers, or with a 

 good manure, all these services are scarcely worthy of notice when com- 

 pared with their labors in the destruction of insects. For this special 

 duty the most essential of their organs have been adapted — their sight is 

 piercing, and even the very smallest among them possess the most extra- 

 ordinary powers of digestion — whilst their great activity and lightness 

 enable them to exercise their calling incessantly, and where most required. 

 The reproductive power of birds and their instinct of migration are also 

 due to the office imposed upon them. When, in the north, the insect 

 world drops into its wintery repose and sleeps under layers of deep snow, 

 then most of the bird tribe fly to the south, there to perform the same 

 duties ; whilst those which remain all the year round in one place gather 

 up the larvae, the eggs, the nests of insects, the few flies or spiders which 

 may be tempted out of their holes by the sun's rays, and the c^leoptera 

 which gnaw the barks of trees." 



That one of the chief objects for which birds were created is to keep' 

 the hosts of insects in check, and thus prevent the too rapid destruction 

 of vegetation, will scarcely be denied by any one. This, then, is, of 

 itself, conclusive evidence that as a whole, in an undisturbed state of nature, 

 they are eminently useful for this purpose, and with the other helps pro- 

 vided by nature will, as a rule, succeed in accomplishing this work. So 

 far as man has been able to look upon undisturbed areas, the facts appear 

 to accord with the theory. But as soon as civilized man enters the field, 

 he commences at once to break up the balance of these contending forces, 

 by destroying the one for food and pleasure, and by producing in abund- 

 ance a small variety of plants which he substitutes for those nature has 

 provided. 



Right here comes up the chief question in this great problem, the 

 one, in fact, upon which its solution hinges. It is this: " Will nature, if 

 permitted to work out results in her own way, allow her flora to be thus 

 disturbed, and yet restore the balance between the obnoxious insects and 

 their enemies? " 



The quotation already made from your lamented co-laborer. Dr. 

 Hull, indicates that he held the negative of this proposition, an opinion 

 which is entertained by a very large number, not only of agriculturists, 

 but also by many naturalists. 



I shall not attempt at present to combat at length this view of the 

 question, nor will I contend even for the truth of a complete affirmative, 

 but will content myself with the presentation of a few suggestions and 

 facts bearing upon it. 



Those vvho hold the negative, as a general rule, maintain that the 

 chief palliative to be found for the evils thus brought upon the agricultur- 

 ists is the natural increase of predaceous and parasitic insects which will 

 ultimately be brought about by the increase of the insect food upon which 

 they feed ; that introduced species, for example, which for a time prove very 

 injurious, will ultimately be followed by their native parasites, or bring 

 to light new ones here which will finally succeed in keeping them in check. 



