No. 7. DEPARTMENT OP AGRICULTURE. 177 



THE BIRDS AND THE FARMERS. 



By HARVEY CLARK, Manns Choice. 



When nature is undisturbed there is kept up a balance between 

 plant and insect life mainly by birds, wbich constitute nature's 

 great check upon the excessive increase of insects. By the process 

 of agriculture man brings together in one area great quantities of 

 certain plants which he uses for food, and in this way furnishes 

 abundant food for certain insects, which often seriously affect the 

 profits of these crops. Thus, we largely lose the balance which 

 nature would maintain, and some means should be taken to increase 

 the number of birds; whereas, on the contrary, the tendency of 

 man's operations has been to destroy the birds, and in that way we 

 can account for the immense damage every now and then by great 

 myriads of noxious insects. The actual benefit birds render to man 

 in destroying insects of all sorts cannot be fixed. It is roughly es- 

 timated that there are about ten times as many species of insects in 

 the world as there are species of all other kinds of animals com- 

 bined — mammals, birds, reptiles, shell-fish, and all the various forms 

 of life. Some writers estimate that the number is twice as great 

 as this — twenty times as many insects as all other forms of ani- 

 mal life. Now, of the aphides (plant lice), one during our ordinary 

 summer, will become the progenitor of 13 generations from the open- 

 ing of spring until the winter kills them off again; and as a rule, 

 there are 100 voung in a brood. 



As to the amount of vegetable matter insects consume, it is cal- 

 culated that an ordinary caterpillar will increase in 30 days from the 

 time it hatches from the egg, about 10,000 times its own size. 



If the increase of the human body during a natural lifetime were 

 in the same ratio as the caterpillar's, man would at the age of ma- 

 turity weigh 40 tons. This gives an idea of the enormous rate of 

 growth of catei'pillars, and, proportionately, the enormous amount 

 of food which they consume. It has been estimated that about 

 10,000 caterpillars could very easily destroy every blade of grass 

 in an acre of cultivate ground. Look at the ravages of potato bugs, 

 army worms, and grasshoppers in the west. They destroy the vege- 

 table matter over wide areas. 

 12—7—1900 



