Man's physical universe

xanabras

752 MAN'S PHYSICAL WELFARE

Insects Are Combated According to Their Methods of Attack.

Certain materials will destroy some insects and be of no avail against

others.

It has been found that insects may be divided into two classes

based on their feeding habits. Those of one class, called chewing

insects, eat the foliage, stems, and roots, while those of the other,

called suckiyig insects, puncture the fruit, leaf, twigs, stems, or

roots to suck the juice. Insecticides are thus classified according to

the type of insect to be attacked, as stomach poisons and contact poisons.

Chemicals are also used as fumigants, baits, and attractants in the

warfare on insects.

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Department of .Agriculture, Bureau of Entomology and Plant Quarantine.)

Various Types of Stomach Poisons Are Used to Kill Insects.

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Arsenical poisons are the most important stomach poisons.

Arsenic

used in such forms as calcium arsenate, lead arsenate, basic copper

arsenate, and Paris green. These products are either sprayed or

dusted on the plants. Unfortunately, they leave residues on food

products which have a cumulatively harmful effect on the human body,

so that the chemist is now called in to determine the amounts to be used

on various fruits and vegetables and to work out methods of removing

the poisons before the products are marketed.^

The use of lead arsenate was first introduced in 1894 by F. C.

Moulton, chemist for the Massachusetts Gypsy Moth Commission.

Since that time its use has increased to millions of pounds a year.

• Consumers should find ways to exert pressure to compel adequate protection from

poisons.

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