88 GENERAL ZOOLOGY 



surface, so that they can get through the exoskeleton, 

 which usually gives protection to the internal organs. 



Perhaps enough has been said to show that the grass- 

 hopper pays the penalty for being abundant and, as in- 

 sects go, to a reasonable degree successful. It is beset by 

 a host of enemies which in various ways try to make an 

 end of it. If we have "put ourselves in the grasshopper's 

 place," we may now feel a certain sympathy for the 

 creature but there is another side to its case. If grass- 

 hoppers have a good season, with abundant food, few 

 enemies and favorable meterological conditions, it will 

 be a bad year for crops. In many parts of the United States 

 in fact, the grasshopper is successful enough to be a con- 

 tinual menace, and in some seasons becomes a veritable 

 calamity. This has led man to devise means for his own 

 protection, and these have been developed along four lines: 

 (1) traps, (2) poisonous sprays, (3) inoculation with diseases 

 or the introduction of natural enemies, and (4) poison 

 baits. 



On certain crops, grasshoppers may be killed by using 

 sprays (arsenate of lead, Paris green, kerosene, etc.). 

 Their method of feeding renders them readily susceptible 

 to poisons sprayed on the outside of plants. Oils, like 

 kerosene, enter the tracheal tubes and kill in that way. 

 Such methods are not, however, readily practised on a 

 comprehensive scale. In large fields trapping is often 

 resorted to as a means of control. One method is to set 

 large cans of water and kerosene below the surface of the 

 ground in places where the insects are most abundant. 

 In hopping about the grasshoppers fall into the traps and 

 are killed. The hopperdozer (Fig. 43) is a movable trap 

 which is driven over infected fields. The grasshoppers 

 hop or fly as it comes near, fall into the kerosene pan, and 

 die. 



In the way of living enemies, a flock of turkeys will do 

 as efficient work as any remedy. Other measures consist 

 in the introduction of parasitic flies, or in the liberation 



