Same species, most of them insects, benefit
increasingly from man 's activities. Modern, large-scale
agriculture offers them a paradise. Crops are grown
year after year in the same or nearby fields, helping
insects populations to build up. Many of the worst
pests are insect invaders from foreign countries that
have left their natural enemies behind and so are as
free as man himself from the check of nature's balance.
Agricultural scientists try hard to find ways to check
insect pests by tricks of cultivation. They import the
ancient enemies of invading foreign insects and foster
the resident enemies of invading foreign insects.