acorn has germinated, it may be entered by a gvuh of the nut weevil (Balatiinits) 

 wliich destroys it, and the more or less empty shell becomes the abiding- ])lace 

 of the larva of the acorn moth. Should, however, the acorn be permitted to 

 i^row, the roots of the young tree may be attacked by the white grubs of root- 

 boring beetles. Escaping these, the oak carpenter worm (Prionoxystus) lays 

 its eggs in cracks and crevices in the bark. On hatching, the worm or borer 

 "perforates a hole the size of a half-inch auger, or large enough to admit the 

 little finger, and requiring three or four years for the bark to close together 

 over it. This hole, running inward to the heart of the tree, and admitting w^ater 

 thereto from every shower that passes, causes a decay in the wood to commence, 

 and the tree never regains its i)revious soundness." (Fitch.) 



Other borers (Buprestidac) feed upon the bark, eating the soft inner layer 

 and the sap, over twenty species of borers and miners being known to infest the 

 trunk of the oak. The limbs and twigs are afifected by the larv?e of certain 

 beetles (Cerambycidae) which act as girdlers or pruners. sometimes severing 

 limbs ten feet in length and over an inch in diameter. (Fitch.) The weevils 

 also bore into the twigs, making an excavation in which the eggs are laid, and 

 the seventeen-year locust stings the branches, making perforations from one to 

 two feet long for the receipt of the eggs 



The limbs and twigs are also afifected by tree hoppers {Mcmhracidac) and 

 oak blights (Aphididae), which puncture them and feed upon their juices, ex- 

 hausting the sap. Some ten species of scale insects, or plant-lice, are known 

 to infest oaks, and over a hundred different species of gallflies are parasitic 

 upon them. 



Oak buds are eaten by the larvse of certain noctuid moths, and oak leaves 

 are injured by caterpillars, basket worms, skippers, miners, weevils, phylloxeras, 

 galls and plant-lice of nearly one hundred and fifty species. 



Altogether over 500 species of insects are known to prey upon the oak, and 

 it is consequently obvious that if they were not in turn preyed upon, oak trees 

 could not exist. But, thanks to the services of birds, as well as to predaceous 

 and parasitic insects, the insectivorous foes of the oak are so held in check that, 

 as a rule, Iheir depredations arc not attended by serious results. Remove these 

 checks, however, and we may expect an immediate and disastrous increase in 

 the enemies of the oak which they so successfully combat. 



Without h'ere attempting to go into detail we may at least mention one 

 or two instances illustrative of the value of birds to trees, ^^'eevils, borers, cat- 

 erpillars, scale insects and plant-lice are all devoured by birds, but it is in eating 

 the eggs of the enemies of the trees that birds perform a service of inestimable 

 value. Prof. C. M. Weed, of the New Hampshire College of Agriculture, in 

 . studying the winter food of the Chickadee, has found that it feeds largely on 

 the eggs of plant-lice. Thus the stomach of a specimen taken December 9, in 

 a mixed growth of pines, maple, willow, and birches, w^as found to contain 429 

 eggs of plant-lice, together with insects of several species. The stomach of 



100 



