310 RELATIONS OF TREES TO BIRDS AND INSECTS. 



threatens to be almost as great a pest to the agriculture 

 of North American soils, breeds in seriously injurious 

 numbers only where a wide extent of surface is bare of 

 woods." 



Some men destroy trees and shrubbery in their borders, 

 because they are supposed to harbor insects. But if this 

 be true, it is because they are not sufficient in extent 

 to shelter the birds that feed upon them. The insects 

 that multiply upon our lands deposit their eggs some in 

 the soil, some on the branches of trees and upon fences 

 and buildings. They are nowise dependent on a wild 

 growth of wood and shrubbery. These pests of agricul- 

 ture need nothing better than the under edge of a clap- 

 board or a shingle whereon to suspend their cocoons or lay 

 their eggs. So minute are the objects that will afford 

 them all the conveniences they need, when hatching and 

 when passing through all their transformations, till they 

 become perfect insects, that no artifice or industry of man 

 can deprive them of their nurseries, or appreciably lessen 

 their numbers. All inventions and appliances used to 

 rid the trees and grounds of these pests never destroyed 

 more than one in a million of their whole number. It is 

 not in the power of man, with all his science, unassisted 

 by birds, to prevent the multiplication of insects from 

 being the cause of his own annihilation. But the farmer, 

 when he destroys the border shrubbery in his fields and 

 the coppice and wood on his hills, exterminates the birds 

 by hosts, while the mischievous boy with his gun destroys 

 only a few individuals. The clipped hedge-row, which is 

 often substituted for a border of wild shrubbery, may 

 assist in breeding insects ; but the birds never build their 

 nests in a hedge-row, unless it be a long-neglected one. 



I have in another essay spoken of the scarcity of birds 

 and other animals in the primitive forest. They are not 

 numerous there, because the forest would yield them only 



