CHAPTER 1\' 



Reasons for the excessive increase of 

 ciestriictive locusts 



\''arions causes may combine to permit of an insect's increas- 

 ing" beyond the norma, thirst of all climatic conditions have to 

 be considered here. These have a great deal to do in the way 

 of favoring or killing off the more or less delicately constructed 

 natural enemies of the hardy species which comprize our most 

 injurious forms. Diseases too, are controlled by climate ; and 

 these latter form an important item in the existence of most 

 insect forms. 



During a succession of abnormally dry years most locusts, 

 whether " native '" or " migratory", are permitted to increase 

 beyond their ordinary numbers. Many of the parasitic insects 

 and other animal-forms which llourish during wet seasons die 

 oft" when the weather becomes dry. By this means several 

 checking influences are removed and the locusts and other 

 insect-pests are permitted to increase untrammeled. 



The excessive increase above normal and non-injurious 

 numbers in the present species can, without doubt, be attributed 

 iirst, to its migratory habit coupled with that of bunching at 

 all times. To these must be added its wintering as a perfect 

 insect in localities selected by itself as guided by an instinct 

 tnat has been developed after years of a nomad life. The cli- 

 matic conditions, too, of the regions most frequented by it dar- 

 ing the greater part of the year are very favorable to so hardy 

 an insect as is our locust. 



By its miuralory liabits and great powers of (light ¡^iinuicn- 



