Checking the Waste: A Study in Conservation

by Mary Huston Gregory

In no country is more harm done by insects than in the United States. The losses to live stock and to plants, both growing and stored, resulting from insects are greater than all the expenses of the National Government, including the pension roll and the yearly maintenance of the army and navy.

Immense as is the value of our farm products, it would be much greater if it were not for the work of these insects. Careful calculations indicate that this loss will amount to not less than the enormous sum of $1,100,000,000 annually and probably far more. The loss is usually estimated at ten per cent. of the crop, but often is much heavier than this, and many indirect losses are not taken into account in this table, though we shall speak of them later.

Most insects pass through four stages: (1) the egg; (2) the worm or larvæ; (3) the chrysalis, cocoon, or pupa; (4) the full-grown insect or imago. Butterflies, moths and beetles are examples of insects in this last stage.

As eggs, they are, of course, harmless, and during the chrysalis state they lie perfectly inactive and are harmless, but many of them are very destructive when they are worms or larvæ, others do most injury in the full-grown state.

The insects that man has most reason to dread are: (1) Plant-lice, tiny insects with soft bodies, usually green. They attach themselves to the stems and leaves of plants and suck their juices, leaving them to wilt and die. They are found on many kinds of plants—on corn, wheat and other grains. They also flourish on garden vegetables and flowers.

(2) Scale insects. These are flat and appear to be only a scale on the stem or fruit. They are usually covered with a hard crust-like covering and are found on trees and bushes. They are usually the color of the bark on which they are found.

(3) Worms and caterpillars are soft-bodied, the bodies being in segments, and either smooth or covered with short bristly hair. They spend nearly all their time in eating, and do immense damage to the foliage of trees and vegetables and to fruit. The adult is a moth or caterpillar. This class is among the farmer's worst insect enemies.

(4) Borers attack trees and tough-stemmed plants. The eggs are laid on the stems, and after hatching, the larvæ bore into the stem or under the bark, causing the foliage to wilt and die. We are all familiar with what we call "worm-eaten" wood, with canals that have been eaten by these borers running through it in all directions. This completely ruins some of the best forest trees for lumber, and makes one of the greatest losses of the forests.

(5) Beetles are insects in the adult state. They have hard, shiny wing-covers. Many of the borers are beetles, and there are other varieties which do great damage, though other kinds are useful to man in destroying harmful insects.

(6) Bugs have their mouth parts prolonged into a sharp beak with which they puncture the skin or bark, instead of chewing the leaves, as do beetles. Flies, gnats, and other similar insects do not usually injure vegetation so much as do some other classes of insects, the principal damage being done to fruits; but they have been found to be the cause of some of the most serious diseases in both man and the lower animals.