BIRDS, CATERPILLARS, AND PLANT LICE. 123 
opportunity to judge for himself as to the value of these 
birds. If this volume does no more than to correct the 
prevalent erroneous impression regarding the relations be- 
tween birds and hairy caterpillars, and call attention to 
the necessity of protecting the birds that eat such larve, it 
will have accomplished something worth while. The ques- 
tion whether or not birds will eat the caterpillars of Bom- 
bycid moths is of vast importance to the Commonwealth, 
the adjoining States, and the nation; for, unless we can 
get help from the natural enemies of the gipsy moth and 
the brown-tail moth, the fight against these insects is likely 
to cost the State many millions of dollars in the end, while 
other States that surely will be invaded must suffer also. 
If it can be shown that birds are capable of doing effective 
work against these insects, it ought not to be difficult to 
create such a public sentiment in favor of bird protection as 
will result in a considerable increase in the numbers of the 
useful species which obtain a part of their sustenance from 
this abundant food supply. 
In May, 1898, injurious insects were unusually prominent 
in the Middlesex Fells. The birches swarmed with aphids ; 
cankerworms appeared on the apple and elm trees; the 
growing webs of tent caterpillars were seen on most of the 
wild apple and wild cherry trees; forest caterpillars were 
gathering on oaks and maples; sawflies, mosquitoes, ants, 
leaf-rollers, and many other injurious species were abun- 
dant. The brown-tail moth was just getting a good foothold 
in the woods, while the ever-present gipsy moth larve were 
beginning to swarm up the trees from the furry egg’ clus- 
ters hidden among the loose stones and seamed ledges of 
the rocky hills. As usual at such times, birds were present 
in large numbers. Wafblers were flitting among the birch 
trees, regaling themselves on countless thousands of plant 
lice, plucking young tent caterpillars from the opening buds 
of wild apple trees or from the fast-forming webs. They 
alighted on the tree trunks and climbed around them, as they 
eagerly sought tiny hairy larve of the gipsy moth, or flut- 
tered in the sunlight as they chased winged gnats in air. 
It seemed that there could be no better opportunity to ob- 
