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fed upon. The Japanese beetle in feeding upon roses, grapes and 
other useful plants becomes an injurious insect, but the lantana- 
feeding insects are beneficial for the reason that the lantana is a 
noxious plant. The silk-worm feeds upon a useful plant, the 
mulberry, and if the silk-worm was not a domesticated insect and 
did not produce the silk of commerce, it would be an injurious 
insect. It is a plant-feeding insect, yet it is a useful insect in 
that it produces something of value to man. It is man's interest 
entirely that decides whether or not an insect is injurious or 
beneficial. 
Let us consider why a plant-feeding insect can work greater 
destruction to a cultivated plant than it can to a plant in the 
state of nature. We have said that in a state of nature a balance 
is maintained. The ravages of insects among cultivated plants 
would indicate that this balance is not maintained under condi- 
tions of cultivation and yet it would seem that a cultivated plant 
had a great advantage. With cultivated plants there is no strug- 
gle for occupation of the soil. The soil is broken up and put in 
a condition favoring germination and growth. Water is given if 
dryness threatens. Fertilizers are added for food. It would seem 
that of all plants, those under cultivation are best fitted to survive, 
that is, grow and produce fruit. Wherein, then, is the disadvan- 
tage? All plants have their insect enemies and always have had. 
By providing for the growth of one plant to the exclusion of all 
others, abundant provision is made for the food of the insect 
enemies of the plant. The conditions have been made favorable 
for the growth of the plant, also, equally favorable for the increase 
of its insect enemies. One of the fundamental principles of life 
is that a particular kind or species shall not predominate to the 
exclusion of all others and the appearance of weeds in a cultivated 
area and the onslaught of insect enemies is but a natural conse- 
quence of man's interference with natural conditions. Another 
fundamental factor that gives the insect enemies the advantage is 
the fact that hardiness and resistance in a wild plant is sacrificed 
for quality in a cultivated plant. The man who can raise a crop 
without an effort to prevent insect injury is the exception. Insect 
injury was called a visitation of God in the dark days. Now it is 
recognized as a natural outcome of cultivation. Every plant has 
its insect enemies and the suppression of these enemies is just as 
distinctly an agricultural operation as plowing, planting, cultivat- 
ing or harvesting. 
We had illustrations in the last lecture of the development of 
an insect, that is, the egg, the larva, the pupa, and the adult. 
The young, or larval stage of development, is one of growth and 
it is during this period, naturallv, that the greater amount of food 
is required. As a group the caterpillars of moths and butterflies 
do an immense amount of damage to plant life. We do not 
always recognize the crawling caterpillar that feeds upon our 
plants as the young of some well-known moth or butterfly. We 
