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 pupse from the leaves, and two 

 larva? 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 pupse from the branches, and ate them. A Yellow-bellied 

 Sapsucker came, and I saw it eat two pupae. It remained at least 

 half an hour more, but I could not see what it was doing. A Yellow- 

 billed Cuckoo ate ten larvae 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 

 larvae, 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 



