Man's physical universe

xanabras

CHEMICAL WARFARE USED TO COMBAT INSECTS 751

United States alone amounts to more than $1,500,000,000. The

Federal Government appropriated somewhat more than $2,182,532

for the fiscal year 1941 for research work for the Bureau of Entomology.

More than $200,000,000 is spent each year in the United States for

insecticides and fumigants.

Armies of insect allies have been drafted to combat insect enemies.

For example, a gnat-sized wasplet has helped a great deal in abating

the ravages of the codling moth. Space will not permit the discussion

of many other examples where beneficial insects are used to control

injurious insects.

The immediate onslaughts of enemy insects must

usually be met by chemicals of various kinds, the nature of which is

determined by the insects being combated.

The majority of insects are harmless, and many of them are of

definite economic importance.

Insects Are Man's Chief Competitors for Foods.

In the grim struggle between man and insects, the latter possess the

advantage of small size, which enables them to live on small quantities

of food and multiply enormously when plenty of food is available.

A large oak tree may support as many as one million insects, while

forest loam may contain as many as fifty million insects per acre.

Insects also possess the advantage of rapid reproduction in large

numbers. For example, a single pair of ladybird beetles could multiply

to 22,000,000,000,000 beetles in six months if conditions were favorable.

The progeny of a single pair of aphids, if they all lived, would be

sufficient at the end of one year to fill up the Atlantic Ocean. The warfare

against insects is

never finished because new legions can replace

their fallen brothers and sisters in a short time.

Insects are superior to man in that they carry lighter weights and

do their work with a smaller expenditure of energy than is possible for

man. There are insects which can live under almost any conditions.

For example, certain insects live in saturated salt water; others live

on deserts or in hot springs.

Insects Transmit Many Important Diseases.

The role that mosquitoes play in spreading malaria, yellow fever,

and elephantiasis is well known. Human lice and rat fleas spread

typhus fever, tsetse flies disseminate sleeping sickness, and houseflies

carry typhoid fever and cholera germs. A long list of diseases carried

by insects could be added to the few given above.

Insects are also carriers of many plant diseases.

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