104 
INSECTS NOXIOUS TO GIIAIN. 
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 vegeta¬ 
bles frequently escape 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. 
For 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 Revo¬ 
lutionary war, the Hessian fly, Cecidomyia destructor , made its 
appearance, and it was so called because it was first observed 
in the year when the Hessian troops were brought over, and 
was popularly supposed to have been accidentally imported 
by those unwelcome strangers. Other destroyers of cereal 
grains have since found their way across the Atlantic, and a 
noxious European aphis has first attacked the American wheat- 
fields within the last four or five years. Unhappily, in these 
cases of migration, the natural corrective of excessive multipli¬ 
cation, the parasitic or voracious enemy of the noxious insect, 
does not always accompany the wanderings of its prey, and 
said fruits, leaves, and herbs, the which shall greatly better the water of 
thy fountains, and hinder the putrefaction thereof.” 
