This historic book may have numerous typos and missing text.
Purchasers can download a free scanned copy of the original book
(without typos) from the publisher. Not indexed. Not illustrated.
1909 Excerpt: ...beneficial action of useful insects.0 CONCLUSION.
That birds do little or no harm by eating insects indiscriminately
may perhaps be better shown by an illustration. Let us suppose that
half of all of the individuals of every species of insect in the
world were suddenly destroyed; haif of the cotton boll weevils,
half of the Colorado potato beetles, half of the chinch bugs, half
of the codling moths, half of the innumerable host of other pests
to the farmer and fruit raiser, and also half of the vast multitude
of predatory and parasitic species swept away at one fell swoop. Is
there any farmer or horticulturist who would not welcome such
destruction? Would it not be a blessing to vegetation as far as
cultivated crops are concerned? Many insects that are now
troublesome would by this reduction be rendered comparatively
innocuous, while in other cases the farmer would be able to cope
successfully with the remainder. Now, this reduction would leave
entirely undisturbed the internal relations of the insects
themselves. The predatory beetles remaining would have
proportionally just as many scales or larvae to feed upon as
before. The parasitic Hymenoptera would have just as many hosts to
infest and the scales and larvae would have just as many enemies to
prey upon them. That a great increase of vegetation would take
place is probable, but this would very soon be counterbalanced by
the unusual supply of food offered to rodents and other herbivorous
mammals, and in fact in a short time the insects themselves would,
through the increased facilities for multiplication, resume their
normal numbers unless there arose some other factor to hold them in
check, such, for instance, as a great increase in the number of
birds. In closing the writer can not do better than...
|Country of origin:
United States Congress
||246 x 189 x 17mm (L x W x T)
||Paperback - Trade
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