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direction, but purely in search of food. They generally march for one day, however, in the direction begun. If the vanguard does change its course, the new direction seems to be communicated in some way to those in the rear, which follow in wave-like form. There sometimes occurs the singular spectacle of two schools crossing each other, the individuals of each keeping to their own course. Some remarkable records have been made of phenomena resulting from the encountering of obstacles to the march. In Europe Dongingk claims to have seen them cross the Dniester for over one German mile, and in layers 7 or 8 inches thick. "In 1875, near Lane, Kansas, they crossed the Pottawatomie Creek, which is about 4 rods wide, by millions; while the Big and Little Blues, tributaries of the Missouri, near Independence, the one about 100 feet wide at its mouth and the other not so wide, were crossed at numerous places by the moving armies, which would march down to the water's edge and commence jumping in, one upon another, till they would pontoon the stream, so as to effect a crossing. Two of these mighty armies also met, one moving east and the other west, on the river bluff, in the same locality, and each turning their course north and down the bluff, and coming to a perpendicular ledge of rock 25 to 30 feet high, passed over in a sheet apparently 6 or 7 inches thick, and causing a roaring noise similar to a cataract of water."1

Their unfledged existence terminates in about 7 weeks. During this time, even without change of direction, they could not travel over 30 miles. The swarms of winged insects will perhaps cover over an average advance of 20 miles a day. They spread most rapidly 4 or 5 days after they become winged, when, with a strong and favorable wind, they may reach a maximum of from 200 to 300 miles a day, and 50 miles per hour. The swarms generally move toward the south and southeast. This locust is single-brooded, dies with the approach of cold weather, and normally hibernates in the egg state. Other kinds of destructive locusts occur, as lesser migratory, non-migratory, redlegged, California devastating, differential, two-striped, pellucid, and American Acridium, but the damage occasioned by these has never been comparable to that caused by the Rocky Mountain species.

1 U. S. Dept. Agr., Div. of Entomol., Bui. 25, pp. 21-22.

Remedies.—Several methods are quite effective in bringing about the destruction of locusts. They have many natural enemies, such as parasitic fungi and insects and birds. These should be protected. Experiments have been made by introducing fungi, especially from South Africa. They were artificially spread, but with little success. Deep fall plowing for the destruction of the eggs is perhaps the best remedy known. In western Colorado "ballooning" used to be practiced. The insects were caught in a large open sack by riding a horse rapidly across the field. A bounty of one cent a pound was paid for the insects, and the rider earned from $5 to $10 per day. Undoubtedly the most effective remedy after the locusts are hatched is to scatter bran or horse droppings poisoned with Paris green around the field before the locusts have entered it.

In Argentina the best results were attained "by the use of torches dipped in tar." The great abundance of locusts in certain years is doubtless the result of a coincidence of climatic conditions favorable to their development and the absence to a great degree of natural destroyers. The Spring Grain Aphis (Toxoptera graminum Rond).—This species, popularly called the "green bug," was first described in 1852, and 30 years later it was discovered in America. It is found most abundantly in the southwest. This pest can be found in the wheat fields during any year, throughout the infested region, but it is rather erratic in its outbreaks. In ordinary seasons it is held in check by its natural enemies. It is extensively parasitized, and lady beetles devour both young and old. It can withstand a lower temperature than its enemies, however, and outbreaks occur after a mild, open winter followed by a late and wet spring. Such outbreaks occurred in 1890, 1900 and 1907. In the south it may breed all winter, and it has an enormous rate of increase. The eggs are laid among the grain plants in the fields. Wheat and rye are the chief foods, but the insect thrives on the other cereals also, and on orchard grass. Late sowing is a preventive measure.

[graphic]

SPRING! GRAIN-APHIS OR GREEN BUG. ENLARGED

Other Insect Enemies.—The most important of these are the wheat straw-worms, the wheat bulb worm, the cut-worms, the joint worm, several species of sawflies, and the army worms. The damage caused is local and not great. Most of them can be more or less controlled.

The total loss from insect enemies of growing wheat is estimated to average at least 20 per cent of the crop. That is, in the absence of attacks from these pests, the wheat crop would have a value approximately $100,000,000 greater than it now has.

General Remedies.—Cultivation upsets the equilibrium established by nature. The resulting environment may be so favorable for the development of an insect as to enable it to multiply beyond all previous proportions. The most obvious remedy is to render the conditions unnatural for the insect concerned. Intelligent control presupposes a working knowledge of the insects to be controlled, and frequently the first step to be taken by the American wheat grower is the gaining of this knowledge. Entomological difficulties must be forecast and forestalled. The state agricultural experiment station or the Department of Agriculture can always aid in this, for there is a fairly effective remedy known for every insect of great importance.

Where such large areas are involved as in wheat raising, remedies must be largely preventive and general. Summer fallowing and crop rotation are the most effective. These result fatally for many insects which are not equipped for encountering the sudden destruction of vegetation, or the abrupt displacing of one kind by another. Even if insects are able to migrate from one field to another, disaster from adverse winds, storms, heat or cold may result to the migrants, especially if they are such frail insects as the Hessian fly or the wheat midge. Good seed should always be sown, and in well prepared soil, for a vigorous crop can best withstand attacks.

Insect Enemies of Stored Wheat.—Several species of insects, popularly known as weevils, cause extensive injury to stored wheat. Commerce has distributed them to all quarters of the globe. In warm climates these insects live an outdoor life, while in the colder parts of the temperate zones they pass an artificial or domestic existence. Not only do they occasion loss in weight, but the grain which they infest is unfit for consumption either by man or by most animals, and cannot be used profitably for seed. Three species of insects injuring stored wheat pass their adolescent stages within the kernel and are universally the most injurious forms. They are the rice and granary weevils and the Angoumois grain moth.

[graphic]

The Granary Weevil (Calandra granaria L.).—From the earliest times this weevil was known as an enemy to stored grain.

It became domesticated ages ago, lost the use of its wings, and is now strictly an indoor species. After the grain of wheat is punctured by the snout of the female, an egg is inserted. The resulting larva makes room for its transforGRANART WEEVIL, ADULT millions within the kernel by deAnd Larva, Enlarged vouring the mealy interior. The grains of most cereals are inhabited by a single larva, but several individuals can thrive in a kernel of maize. The length of the life cycle and the number of generations annually produced depend on season and climate. In southern United States there may be six or more generations per year. One pair is estimated to produce 6,000 descendants in a single year. Besides wheat, they attack all the other grains, and the chick-pea. The greatest damage is caused by the long-lived adults, which gnaw into the kernels for food and shelter.

The Rice Weevil (Calandra oryza L.) resembles the granary weevil in structure and habits. It differs from the granary weevil most essentially in having well developed wings, and consequently being often found in the field. It lays its eggs in the standing grain in the tropics, and in the extreme south of the United States, where it is erroneously called "black weevil." It originated in India, was first found in rice, and is now established in most of the grain growing countries of the world.

The Angoumois Grain Moth (Sitotroga cerealella 01.).—Since 1736 the injuries of this moth have been noticed in the province of Angoumois, France, from which it received its name. In the United States it was noticed as early as 1728, and is often incorrectly called "tly weevil." It is widely spread and does incalculable damage in the southern states. It is rapidly spreading, and where it has become established it is more injurious than the weevils, also attacking grain in the field as far north as central Pennsylvania.

The adult insect is often mistaken for a clothes moth. The eggs are deposited in standing grain and in the bin, singly or in clusters of from 20 to 30. It requires at least 4 days for the eggs to hatch. The minute larva? or caterpillars burrow into the kernels for food, and in 3 weeks or j£2£S£2£& "ffH ni"ro they are matured. A silken cocoon is "'■'then spun within the kernel, the caterpillar transforms to a pupa or chrysalis, and in

GRAIN MOTH, ADULT a few days ^ moth is ^^ m y^ wing

In favorable weather the life cycle requires

ENLARGED c i j u ± o i

o weeks, and about 8 generations are produced annually in the south, where the insect breeds all winter.

The Mediterranean Flour Moth (Ephestia kuehniella Zell.)—The most important of all mill insects, it was comparatively unknown before 1877, when it was discovered in Germany. Its appearance was noticed in England in 1886, in Canada in 1889, in California in 1892, and in New York and Pennsylvania in 1895. While its range is yet limited, it is rapidly becoming distributed throughout the civilized world. The high and equable temperature maintained in modern mills has made the insect a formidable one, for this condition is highly favorable to its development.

Cylindrical silken tubes are formed by the caterpillars. They feed in these until full growth is attained, when a new silken domicile is formed. This becomes a cocoon in which occur the transformations to pupa and imago. In the warmest weather the life cycle is passed in 38 days. It is the habit of web spinning that renders the insect most injurious. Infested flour is soon felted together so as to clog the milling machinery, necessitating prolonged and costly stoppage. Flour or meal is preferred by the larva, but in the absence of these it attacks grain, and it flourishes on bran and all prepared cereal foods,

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