In a recent lecture, Prof. Witmer Stone, of Philadelphia, cited many facts to show that birds are nature's great check on the excess of insects, and that they keep the balance between plants and insect life. Ten thousand caterpillars, it has been estimated, could destroy every blade of grass on an acre of cultivated ground. In thirty days from the time it is hatched an ordinary caterpillar increases 10,000 times in bulk, and the food it lives and grows on is vegetable. The insect population of a single cherry tree infested with aphides was calculated by a prominent entomologist at no less than twelve million. The bird population of cultivated country districts has been estimated at from seven hundred to one thousand per square mile. This is small compared with the number of insects, yet as each bird consumes hundreds of insects every day, the latter are prevented from becoming the scourge they would be but for their feathered enemies. Mr. E. H. Forbush, Ornithologist of the Board of Agriculture of Massachusetts, states that the stomachs of four chickadees contained 1,028 eggs of the cankerworm. The stomachs of four other birds of the same species contained about 600 eggs and 105 female moths of the cankerworm. The average number of eggs found in twenty of these moths was 185; and as it is estimated that a chickadee may eat thirty female cankerworm moths per day during the twenty-five days which these moths crawl up trees, it follows that in this period each chickadee would destroy 138,750 eggs of this noxious insect. A pamphlet issued by the Department of Agriculture of the United States says that the cuckoo, which is common in all the Eastern States, has been conclusively shown to be much given to eating caterpillars, and, unlike most birds, does not reject those that are covered with hair. In fact, cuckoos eat so many hairy caterpillars that the hairs pierce the inner lining of their stomach and remain there, so that when the stomach is opened and turned inside out, it appears to be lined with a thin coating of hair. This bird also eats beetles, grasshoppers, sawflies, and spiders. It turns out from the investigations of the department that the suspicion with which all farmers look upon woodpeckers is undeserved by that bird. These birds rarely leave an important mark upon a healthy tree, but when a tree is affected by wood-boring larvae the insects are accurately located, dislodged, and devoured. In case the holes from which the borers are taken are afterward occupied and enlarged by colonies of ants, these ants are drawn out and eaten. Woodpeckers are great conservators of forests, and to them more than to any other agency is due the preservation of timber from hordes of destructive insects.