MODERN WARFARE AGAINST GRASSHOPPERS 473 



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 im- 

 possible. 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 grass- 

 hoppers 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 sum- 

 mer 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 obser- 

 vations 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- 



