RELATIONS OF TREES TO BIRDS AND INSECTS. 309 



I have often thought of my neighbor's remarks, especial- 

 ly when I have observed the diligence of our farmers in 

 destroying upon their grounds every acceptable harbor for 

 the birds. When we are traversing a wood, if we discover 

 an apple-tree growing in a little clearing or open space, 

 we find it invariably exempt from the ravages of the 

 common apple-borer. The same exemption is observed 

 in those fruit-trees that stand very near a wild wood, or 

 any wood containing a spontaneous undergrowth. The 

 explanation of this fact is that the wood affords a harbor 

 to the birds that destroy these insects in all their forms. 

 Orchards and gardens, on the contrary, which are located 

 at any considerable distance from a wood, have not this 

 security. Eobins, it is true, are very abundant in or- 

 chards, which are their breeding-places ; but robins, though 

 the most useful birds that are known to exist, take all 

 their food from the ground. They destroy vast quantities 

 of cutworms and chrysalids buried in the soil, but they 

 take no part of their insect food from the trees. The 

 birds that perform this work are the sylvias, woodpeckers 

 creepers, and other species that live only in woods and 

 thickets. Hence an orchard that is nearly surrounded by 

 a wild wood of much extent is not badly infested by 

 borers and other injurious insects. 



All species of insects multiply in cultivated grounds, 

 while the birds, with a few exceptions, that feed upon 

 them, can find a nursery and protection only in the woods. 

 " The locust," says George P. Marsh, " which ravages the 

 East with its voracious armies, is bred in vast open 

 plains, which admit the full heat of the sun to hasten 

 the hatching of the eggs, gather no moisture to destroy 

 them, and harbor no bird to feed upon their larvae. It is 

 only since the felling of the forests of Asia Minor and 

 Gyrene that the locust has become so fearfully destructive 

 in those countries ; and the grasshopper, which now 



