Nearly all the common birds feed freely upon the cankerworm, and benefit the orchard in so doing. The chickadee is perhaps the most useful. A recent writer is very positive that each chickadee will devour on an average thirty female cankerworm moths a day; and that if the average number of eggs laid by each female is one hundred and eighty-five, one chickadee would thus destroy in one day five thousand five hundred and fifty eggs, and, in the twenty-five days in which the cankerworm moths crawl up the tree, would rid the orchard of one hundred and thirty-eight thousand seven hundred and fifty. These birds also eat immense numbers of cankerworm eggs before they hatch into worms. [Illustration: FIG. 158. EGGS OF THE FALL CANKERWORM] _Treatment._ The inability of the female to fly gives us an easy way to prevent the larval offspring from getting to the foliage of our trees, for we know that the only highway open to her or her larvae leads up the trunk. We must obstruct this highway so that no crawling creature may pass. This is readily done by smoothing the bark and fitting close to it a band of paper, and making sure that it is tight enough to prevent anything from crawling underneath. Then smear over the paper something so sticky that any moth or larva that attempts to pass will be entangled. Printer's ink will do very well, or you can buy either dendrolene or tanglefoot. [Illustration: FIG. 159. APPLE-TREE TENT CATERPILLAR _a_, eggs; _b_, cocoon; _c_, caterpillar] Encourage the chickadee and all other birds, except the English sparrow, to stay in your orchard. This is easily done by feeding and protecting them in their times of need. =The Apple-Tree Tent Caterpillar.= The apple-tree tent caterpillar is a larva so well known that you only need to be told how to guard against it. The mother of this caterpillar is a reddish moth. This insect passes the winter in the egg state securely fastened on the twigs as shown in Fig. 159, _a_. _Treatment._ There are three principal methods, (1) Destroy the eggs. The egg masses are readily seen in winter and may easily be collected and burned by boys. The chickadee eats great quantities of these eggs. (2) With torches burn the nests at dusk when all the worms are within. You must be very careful in burning or you will harm the young branches with their tender bark. (3) Encourage the residence of birds. Urge your neighbors to make war on the larvae, too, since the pest spreads rapidly from farm to farm. Regularly sprayed orchards are rarely troubled by this pest. [Illustration: FIG. 160. THE TWIG GIRDLER AT ITS DESTRUCTIVE WORK _a_, the girdler; _b_, the egg-hole; _c_, the groove cut by girdler; _e_, the egg] =The Twig Girdler.= The twig girdler lays her eggs in the twigs of pear, pecan, apple, and other trees. It is necessary that the larvae develop in dead wood. This the mother provides by girdling the twig so deeply that it will die and fall to the ground.