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 larve of poly- 
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 larvee 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 grant 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 river 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 
