32 USEFUL BIRDS. 
mine with approximate accuracy the numbers of insects that 
infest our forest trees. The forest insects of some sections 
of Europe have been studied longer, and the numbers of in- 
sects found injuring the principal 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-cight. 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 number 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 (Diplosis tritici), 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 Shade Trees, by A. S. Packard. Fifth Report 
of the United States Entomological Commission, 1886-90, p. 48. 
3 Report on the Rocky Mountain Locust, by A. S. Packard. Ninth Annual 
Report of the United States Geological and Geographical Survey of the Territo- 
Ties, 1875, p. 709. 
