They obtain the mussel eggs, and when they are hatched place them in the pools with the fish from the overflowed lands. The tiny mussel larvae attach themselves to the fish and are carried to the rivers and ponds with the fish. Soon they are ready to drop to the bottom and find food for themselves.

In this way 25,000,000 mussels were carried last year to streams where mussels are known to thrive. If these mussel-bearing fish can be obtained by farmers having private fish ponds, the ponds can be drained each year and the mussels gathered, thus adding considerably to the owner's income, and also keeping up the pearl b.u.t.ton industry, in addition to the food supply which he gains from the fish.

Enough has been said to show clearly how desirable and how possible it is to conserve and increase our fish supplies. With the cooperation of all who waste the fish at present, and those who might aid in stocking the streams, we could add greatly to the food supply of the nation at a less cost than in any other way.

REFERENCES

Grazing Lands. Report National Conservation Commission.

Grazing on the Public Lands. (Jastro.) Report Governor's Conference.

The Grazing Lands and Public Forests of Arizona. (Heard.) Report Governor's Conference.

Grazing Problems in the Southwest and How to Meet Them. Bulletin, Dept.

of Agriculture, 5c.

Reports of the Bureau of Animal Industry. Dept. of Agriculture.

Distribution of Fish and Fish Eggs. Dept. Commerce and Labor.[B]

[Footnote B: All Bureau and Commission reports are free.]

Reports of the Commission of Fisheries.

National Fisheries Congress.

CHAPTER X

INSECTS

If we look at a watch, we see that one wheel can not move until the one next in order to it moves, and that, in turn, must be set in motion by another wheel. In the same way nature adjusts itself in its various parts. Before man enters a region, the balance is perfect. Plants crowd each other out of the way, the weaker giving place to the stronger; then insects come to destroy them. These insects are destroyed by birds, small mammals or other insects. The birds are killed by animals and other birds, which in turn are the food of larger animals. And so through all nature runs this law of balance; nothing increases in too great a proportion.

But when man comes, he thinks only of his own needs and wishes and begins at once to upset the delicate balance. Year after year, he plants large fields of a single crop, and, calling other plants weeds, because they hinder the growth of his grain, he drives them out entirely. The insects that feed on these plants, finding no food, soon disappear, while the ones which feed on the farmers' crops, finding food so plentiful, are able to increase in great numbers. They increase all the more rapidly because man, not knowing or not caring to know who his real helpers are, has killed and driven away the birds that would feed on them.

In order to readjust matters, he must learn how to destroy the insects, or he can not have crops. Both the plant enemies, the weeds, and the insects are always trying to bring about nature's balance again by driving out the over-abundant field crop, so he must constantly fight them in order to secure his harvest.

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 pa.s.s through four stages: (1) the egg; (2) the worm or larvae; (3) the chrysalis, coc.o.o.n, or pupa; (4) the full-grown insect or imago. b.u.t.terflies, 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 larvae, 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 cla.s.s 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 larvae 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 ca.n.a.ls 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 cla.s.ses of insects, the princ.i.p.al 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.

The Department of Agriculture divides the injuries done by insects into cla.s.ses according to the products injured, and in the list they place first the injury done to cereal crops.

The insects which damage the corn crop most seriously are the corn-root worm, which feeds on the roots of young corn, causing it to fall over and die, and which sometimes takes the whole corn crop of a large region. The next most important is the boll-worm or ear-worm. Most persons have seen this worm in the ears of sweet corn; ninety ears out of every hundred contain a worm which destroys from one-tenth to one-half the corn. Some years every ear in large regions is infested. In the South the field corn is attacked as badly as the sweet corn, but in the great corn states the injury is much less. Even here, however, the total loss is very great.

Almost equally important is the damage wrought by the chinch-bug, which is also one of the greatest pests in wheat and oats.

Every year in different sections of the country, bill-bugs, wire-worms, cutworms, cornstalk borers, locusts, gra.s.shoppers, corn plant-lice and other insects, destroy millions of bushels of corn.

Of the cereal crops, wheat suffers most from insects. Of the large number of insects that attack wheat, the three important species are the Hessian fly, the chinch-bug and the grain plant-louse or green-bug.

The Hessian fly has been known to destroy as much as sixty per cent. of all the wheat acreage of a state. Fortunately, this damage is done early in the year, so that when whole fields are destroyed they can be replanted with other crops and only the cost of seed and labor is to be counted as a loss. But more often the field is only partly destroyed by the fly; it is not necessary to replant, but the yield is small, often not more than one-third. Some years the loss from the Hessian fly is very heavy, at other times comparatively light, yet there are few years when the loss is less than ten per cent. of the total crop from this insect alone,--which meant last year a loss of 72,500,000 bushels.

The chinch-bug is responsible for the loss of five per cent., or one bushel out of every twenty. It attacks the straw, causing the heads of wheat to fall over and wither away.

The injury done by the green-bug comes just as the wheat begins to ripen, the tiny green creatures attaching themselves in great numbers to the heads of the wheat. Other insects which prey on the wheat crop are gra.s.shoppers, the wheat midge, cutworms and army-worms.

If it were not for the attacks of these various pests the wheat crop would be at least one-fifth larger than it is. Instead of 725,000,000 bushels, it would be 870,000,000; which, with wheat at a dollar a bushel, amounts to a loss of nearly $150,000,000. Further, the world loses all this valuable bread-stuff.

Oats, rye and barley suffer far less than wheat from insect ravages but they are all attacked by the same insects, and on the whole, much damage is done to them each year.

Hay, clover, and alfalfa have their enemies which destroy a considerable part of the crops. The locusts and caterpillars, the army-worms and cutworms are the best known, but the tiny leaf-hoppers, which spring up at every step as we walk across the path or lawn, and the web-worms and gra.s.s-worms and grubs which work about the roots of the plants all do their part in lowering the production.

The princ.i.p.al insect enemies of cotton are the cotton boll-weevil, the boll-worm, the cotton red spider, and the cotton-leaf worm. The control of the boll-weevil is considered one of the most serious problems confronting the agricultural men of the country. In the first years after its introduction, it reduced the cotton crop fully fifty per cent., and was the cause, not only of serious loss to the farmers, but of the closing of the cotton mills in New England, of a scarcity of cotton cloth and a decided rise in its price. The boll-weevil is a beetle about a quarter of an inch in length. This little beetle eats into the heart of each boll, which soon falls to the ground.

The cotton-leaf worm formerly caused heavy damage, as much as $20,000,000 to $30,000,000 a year, but the loss has been greatly reduced by the war which farmers have waged against it. It is still estimated at from $5,000,000 to $10,000,000.

The boll-worm is chiefly destructive in the Southwest and does damage to the extent of $12,000,000.

All in all no article of commerce is more seriously affected by insect ravages than cotton, on account of its necessity, and the fact that it can be raised only in certain regions.

Tobacco is one of the princ.i.p.al crops in several states and it suffers heavily from insect damage. The large, showy tobacco-worm and the tiny tobacco-thrips cause serious injury to the leaves.

Sugar-cane has its insect enemies which take on an average one stalk out of every ten raised in this country, and reduce the crop in the same proportion.

The cranberry is another valuable commercial plant that has been greatly affected by an insect known as the cranberry fruit worm, but by spraying, growers have been able to reduce the damage from sixty per cent. down to fourteen per cent.

Garden vegetables suffer more than anything else from insects. Potatoes are attacked by two species of insects, both destructive unless held in check. One is the reddish brown blister-beetle. The eggs are laid on the ground, and do not become adult insects until the second year. The other is the striped Colorado beetle, the eggs of which are laid on the under side of the leaves, and develop into adults in a short time. Two broods of this beetle develop in a single season. Thus it may be seen that the two are entirely different, though they are often supposed to be the same. The Colorado beetle, by the immense damage it was doing to a necessary food crop, first led to a regular method of fighting insects in this country. This potato-bug is not feared as it was in the past, since farmers have learned to control it in a great measure, but they have only been able to lessen the evil, never to drive it out completely.