UTILITY OF BIRDS IN WOODLANDS. 109 



to shoot the birds which thus penetrated into his enclosures 

 for the purpose of eating the worms. Although the land on 

 all sides sustained a good growth of huckleberry bushes, 

 he never found the berries in the stomachs of the birds he 

 killed, but always found insects. He said that birds came from 

 all quarters to destroy his silkworms. To test the destruc- 

 tiveness of the birds, he placed two thousand larvae of Jpoly- 

 phemus on a scrub oak near his door. In a few days the 

 Robins and Catbirds had eaten them all. His experience of 

 several years in rearing the silkworm led him to the belief 

 that, were the birds to be killed off, all vegetation would be 

 destroyed. Such experiences show the difficulty of rearing 

 caterpillars, even under artificial protection, in a land fre- 

 quented by arboreal birds, and explain the rarity of serious 

 injury by such larvae in our woods. 



The rapidity with which caterpillars propagate where 

 there are no such birds, and their destructiveness under such 

 circumstances, may be shown by the experience of many 

 settlers in their attempts to establish groves on the open 

 prairies. It has been the beneficent policy of our govern- 

 ment to gi-ant certain tracts of land (tree claims) to settlers, 

 provided they would plant trees. This was done with the 

 purpose of providing wind-breaks on the prairies, which 

 would eventually furnish the people with a supply of wood 

 and lumber. At first, however, this work met with little 

 success, for there were few tree-loving birds in the prairie 

 country except along the timbered i-iver bottoms. The set- 

 tlers introduced insect pests on imported trees. The ene- 

 . mies of tree insects being absent, because the country was 

 destitute of well-grown groves and orchards, the insects 

 multiplied and overran the seedling trees ; the larger moths, 

 like cecropia and polyphemus, were the worst pests of all, 

 increasing rapidly, eating voraciously, and making it almost 

 impossible to raise trees. Dr. Lawrence Bruner, in a paper 

 on insects injurious to tree claims, states that the absence 

 alone of so great a factor as tree-loving birds in keeping 

 down insect pests and ridding the country of them soon 

 becomes apparent in the great increase and consequent dam- 

 age done by these pests. He asserts, also, that as an enemy 



