ECONOMIC VALUE OF BIRDS TO THE STATE, II9 



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

 of the oak. The limbs and twigs are affected by the larvae of certain beetles {Ccr- 

 ainbycidce) 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 arc 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 affected by tree hoppers {ManbracidcB) and oak 

 blights {Aphididm), which puncture them and feed upon their juices, exhausting 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 larvae 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, their 

 depredations are 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 here attempting to go into detail we may at least mention one or two 

 instances illustrative of the value of birds to trees. Weevils, borers, caterpillars, 

 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, was found to contain 429 eggs of plant-lice, together with 

 insects of several species. The stomach of another Chickadee taken February 26 

 in a growth of pines and birches, contained 454 eggs of Aphides, an equal percentage 

 (44) of what seemed to be dried castings from the old nests of tent-caterpillars, 

 spiders' eggs, and eggs of the canker-worm. 



Additional statistics of the forest haunting birds' food are given under the 

 proper head, but we should call especial attention here to the great value to trees of 

 our Cuckoos in devouring caterpillars. Over 48 per cent of the food of Cuckoos 

 has been found by Professor Beal, of the U. S. Department of Agriculture, to con- 



