Page:Popular Science Monthly Volume 81.djvu/479

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473
MODERN WARFARE AGAINST GRASSHOPPERS

to be hoped that this difficulty, the chief obstacle in connection with spraying, will be overcome.

While advising spraying, we do not lose sight of the older methods, more or less effective, that entomologists have been urging upon farmers in years past: the old time "hopper-dozer" with kerosene in the pan, late fall plowing, a flock of turkeys to protect the garden, etc. Our work, however, has resulted in throwing doubt upon the effectiveness of some of the generally accepted methods and has made it necessary to qualify statements made in all good faith from time immemorial. For example, the entomologist, when the farmer has declared that a large number of grasshoppers jump out of the hopper-dozer and are not killed, assuming an air of wisdom, has said, "No, if they only touch the kerosene they are bound to die, even if they appear to have escaped destruction at the time." Last summer's work has made it evident that this is only true of the short-winged forms, in which the oil can reach the spiracles; in others, where the wings cover these breathing openings and protect them as well as the body of the insect, they live to carry on the work of destruction. Again, farmers living in grasshopper-infested regions generally handle so much land that late fall plowing is impossible. As a rule, they begin to plow, in the latitude of Minnesota at least, in August, as soon as the crop is off the ground and the grasshoppers find no better place to deposit their eggs than in the plowed stubble.

Further, this advice is based largely upon the theory that if the "pocket" or capsule containing the eggs is turned upside down, or nearly so, the newly hatched hopper never gets out and perishes. It appears, however, that this view, accepted as a truth by each succeeding generation of entomologists, must be modified, for it is probable that the capsule, becoming soft and gelatinous by the action of the elements, or perhaps disappearing altogether by May, offers no obstacle to the imprisoned insect, and still further, we have no positive proof that the newly-hatched hopper can not ascend through many inches of the soil until the surface is reached. Laboratory experiments during the summer of 1912 indicate that the newly-hatched grasshopper may work his way through eight inches of fairly well packed soil.

Finally, it has been commonly believed, and is doubtless true of the majority of insects, that alternate freezing and thawing is fatal. But one of the field men exposed last winter about twenty young hoppers, hatched in the warmth of indoors, to alternately a freezing and thawing temperature several times, with no bad results to the insects, one only succumbing and that probably being injured in handling. These observations appear to leave open a large field for investigation along the lines of grasshopper control.

Grasshoppers have many enemies, but their numbers are so enor-