BIRDS, CATERPILLARS, AND PLANT LICE. 147 
in a tree near the edge of the colony, sang for a few minutes, then flew 
to the sprouts that are infested, then to the ground. He scratched in 
the leaves, and I saw him take seven pupz from the leaves, and two 
larvee that were crawling on the ground. There was a pair of Great- 
crested Flycatchers coming and going all day. They took a great many 
male moths, and I saw them take five female moths from the tree 
trunks. _A Robin perched in the tops of the oak trees, picked off four- 
teen of the pupze from the branches, and ate them. A Yellow-bellied 
Sapsucker came, and I saw it eat two pupx. It remained at least 
half an hour more, but I could not see what it was doing. A Yellow- 
billed Cuckoo ate ten larvee in a few minutes. 
Thousands of these insects are undoubtedly eaten by birds, 
for every one that they are seen to eat ; but, it may be asked, 
if the birds are effective enemies of these introduced gipsy 
larvee, why have they not kept down the increase of these 
insects? To this it must be answered that we have not birds 
enough, nor are there likely ever to be enough, to do away 
with these pests entirely, unless birds learn to eat the eggs. 
Other natural enemies must also help in this work, if we are 
‘to see an end of the moth plague; but there is little that we 
can do to protect the insect enemies of the moth or to insure 
their multiplication, while we can protect and feed the birds, 
and so secure an increase in their numbers. In so far as 
we are able to take measures that will result in increasing 
the numbers of certain birds, just so far shall we be able to 
prevent the increase of destructive insects. As time goes 
on, it is probable that birds will become more and more effi- 
cient as enemies of the gipsy moth and the brown-tail moth, 
as they learn better how to manage them. It seemed appar- 
ent that they had not learned to eat the eggs of the gipsy 
moth up to 1896, when my last studies on that subject were 
made; still, now that ten years have passed, the subject 
should be investigated again. It is quite possible that by 
this time. some birds may have learned that these eggs are 
good for food. As the gipsy moth spends more than half 
the year in the egg, this is its most vulnerable point. If 
Jays, Creepers, Nuthatches, Woodpeckers, and other birds 
could learn to eat these eggs, as European birds are said to 
do, they would then have an increased food supply the year 
round. Naturally they would increase in numbers, and thus 
