32 USEFUL BIRDS. 



mine with approximate accuracy the numbers of insects that 

 infest oiu" forest trees. The forest insects of some sections 

 of Europe have been studied longer, and the numbers of in- 

 sects found injurino- the })rincipal trees are surprising. Kal- 

 tenbach enumerates five hundred and thirty-seven species 

 of insects, from central Europe, injurious to the oak ; to the 

 elm he ascribes one hundred and seven. The poplars feed 

 two hundred and sixty-four species ; the willows harbor 

 three hundred and ninety-six ; the birches, two hundred and 

 seventy; the alder, one hundred and nineteen; the beech, 

 one hundred and fifty-four ; the hazel, ninety-seven ; and 

 the hornbeam, eighty-eight. Among the coniferous trees, 

 the pines, larch, spruce, and fir, collectively, are attacked 

 by two hundred and ninety-nine species of insects.^ 



Dr. Packard enumerated over four hundred species which 

 prey upon our oaks, and believed it not improbable that 

 ultimately the luunber of species found on the oaks of the 

 United States would be from six hundred to eight hundred 

 or even one thousand. ^ 



The list of insects which feed on grasses, cereals, field and 

 garden crops is very large and constantly growing, for it is 

 continually receiving accessions from both native and foreign 

 sources. The destructiveness of some of these insects is so 

 enormous and widespread that the financial loss resulting 

 therefrom amounts to a heavy annual tax on the people of 

 the United States. Hence since the first settlement of the 

 country the amount of this annual tax has been increasing. 



In 1854 the loss in New York State alone from the ravages 

 of the insignificant wheat midge (Diplo.ns fritici), as esti- 

 mated by the secretary of the New York State Agricultural 

 Society, was fifteen million dollars. Whole fields of wheat 

 were left ungarnered. So destructive was this insect in the 

 following years as to stop the raising of white wheat, and 

 reduce the value of all wheat lands forty per cent.^ 



' Die Pflanzenfeinde aus der Klasse der Insekten. 



■ Insects Injurious to Forest and Sliade Trees, hy A. S. Packard. Fifth Report 

 of the United States Entomological Commission, 1886-90, p. 48. 



^ Report on the Rocky Mountain Locust, by A. S. Packard. Ninth Annual 

 Report of the United States Geological and Geographical Survey of the Territo- 

 ries, 1875, p. 709. 



