134 INTRODUCTION OF INSECTS. 
Introduction of Insects. 
The general tendency of man’s encroachments upon spon- 
taneous nature has been to increase insect life at the expense 
of vegetation and of the smaller quadrupeds and _ birds. 
Doubtless there are insects in all woods, but in temperate 
climates they are comparatively few and harmless, and the 
most numerous tribes which breed in the forest, or rather in its 
waters, and indeed in all solitudes, are those which little injure 
vegetation, such as mosquitoes, gnats, and the like. With 
the cultivated plants of man come the myriad tribes which 
feed or breed upon them, and agriculture not only introduces 
new species, but so multiplies the number of individuals as to 
defy calculation. Newly introduced vegetables frequently es- 
cape for years the insect plagues which had infested them in 
their native habitat; but the importation of other varieties of 
the plant, the exchange of seed, or some mere accident, is sure 
in the long run to carry the egg, the larva, or the chrysalis to 
the most distant shores where the plant assigned to it by nature 
as its possession has preceded it. ‘or many years after the 
colonization of the United States, few or none of the insects 
which attack wheat in its different stages of growth, were 
known in America. During the Revolutionary war, the Hes- 
and they become destructive to the forest because they are driven to the 
living tree for nutriment and cover. The forest of Fontainebleau is almost 
wholly without birds, and their absence is ascribed by some writers to the 
want of water, which, in the thirsty sands of that wood, does not gather into 
running brooks; but the want of undergrowth is perhaps an equally good 
reason for their scarcity. 
On the other hand, the thinning out of the forest and the removal of under- 
wood and decayed timber, by which it is brought more nearly to the condition 
of an artificial wood, is often destructive to insect tribes which, though not 
injurious to trees, are noxious to man. ‘Thus the troublesome woodtick, 
formerly very abundant in the North Eastern, as it unhappily still is in native 
forests in the Southern and Western States, has become nearly or quite extinct 
in the former region since the woods have been reduced in extent and laid 
more open to the sun and air.—Asa Fire, in Report of New York Agricultural 
Society for 1870, pp. 863, 364. 
