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regions. From 1889 to 1897 they wrought frightful havoc in Argentina, visiting 347,000,000 acres in the latter year, and destroying 30 per cent of the crops. From 1897 to 1900 the Argentine government spent over $7,000,000 in an attempt to exterminate them. The limit of the invaded region was steadily pushed northward, until in 1901 locusts were entirely absent from the wheat area. They came into Argentina from Bolivia, the territory of the Chaco, and western Brazil. Barcelona, Spain, reported a plague of locusts spreading in 1902. In west central Asia, between Askabad and Krasnovodsk, the cereal and cotton crops are commonly devastated by locusts. In 1903, 50,000 roubles were set aside to be devoted to the destruction of the insects' eggs in trans-Caspia. It is claimed that sacked flour piled on open railway trucks near Krasnovodsk was devoured by clouds of rapacious locusts in an incredibly short time.1 In the United States during the early seventies the grass
Wheat Plant-louse: a, Winged Adult; 6, Female; C, Nymph.
hoppers used to invade Kansas "so they would block railroad trains and destroy all vegetation."' In the Red river valley they appeared in great clouds which "cleaned the country quite thoroughly on their flight.''3 These invasions seem to have come mainly from the permanent breeding grounds of the Rocky Mountain locust (Caloptenus spretus Uhler). These grounds were located approximately between the meridians of 102 and 112 degrees, and between the 40th and 55th parallels.
1 Mo. Sum. Commerce and Finance, Feb., 1904, p. 2818.
2 Industrial Commission, 10:759.
8 Proc. Tri-State Grain Growers' Ass'n. 1900, p. 184.
East of this territory was a frequently invaded strip about five degrees in width. A great scope of territory farther east, south and west was periodically visited when the natural conditions on the permanent breeding grounds were such as to produce myriads of grasshoppers. They could live only one generation on the lower lands, and then perished. Large portions of their grounds are now cultivated, and this restricts their multiplication. It is thus perhaps impossible for such overwhelming swarms to occur as formerly. Such swarms as do occasionally appear are more localized, and not of such uncontrollable magnitude. They may still be relatively abundant, however. During 1901 in Canada, several hundred insects could be seen "to the yard," and "dead locusts could be gathered up in wagon loads and at times be smelt for half a mile," after poison had been used. In Montana they frequently devastate ranges so that the herds must seek pasture elsewhere.
The Rocky Mountain Locust lays its eggs in almost any kind of soil, preferably in bare, sandy places on high and dry ground. They are laid chiefly in the first inch of soil, and in masses or pods surrounded by a mucous fluid, each pod containing about 30 eggs. The average laying season extends over 6 to 10 weeks, and about 3 egg masses are formed by each female. The time of hatching depends entirely on the climate and latitude. While the young locust is very active, it will remain almost stationary
if food is plenty. The migrating propensity is developed only after the first molt, and frequently not until after the second or third. When food becomes scarce the locusts migrate, often in a body a mile wide. From the very first they conROCKY Mountain Grass- gregate and display gregarious inHopper; a, Pupa; b, Full st,ncts- They feed as they advance, Grown Larva; C, Young louring everything in their path. Labva. Natural Size. « they are n"merous enough to devastate a region, they are forced to feed upon one another, and immense numbers perish from debility and starvation. They usually move only during the warmer hours of the day, and in no particular 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.'' *
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.
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,