CONTENTS. xiii 



SALTATORIA. 

 CHAPTER V. 



LOCUSTS AND GRASSHOPPERS 



Series Cursoria and Saltatoria To two families of latter, term Grass- 

 hopper applied Acridiidae, prominent characteristics Anatomy 

 Organs of special sense Air-sacs Acridiidae remarkable amongst 

 Orthoptera for possession of Arrangement in Rocky Mountain 

 Locust Use Locust an aeronaut To this fact largely due its 

 enormous powers of flight Dilatable tracheae Locust, how en- 

 dowed intellectually Gift of " song " Of great importance to the 

 creatures Apparatus for producing sound The music, charac- 

 teristic of male Stridulation during flight Acridian ears Three 

 forms Minute structure Ears in both sexes, as in most species 

 Function of acoustic organs difficult to determine Possible solu- 

 tion of difficulty Oviposition ; and philosophy of egg-mass 

 Migratory locusts may make a deposit of eggs at more than one 

 place during migration Egg-enemies Process of escape of the 

 young from the egg, of much interest Post-embryonic develop- 

 ment of Acridiidae Change of colour in course of development ... 81 



CHAPTER VI. 



LOCUSTS AND GRASSHOPPERS (ACRIDIID^) continued. 



Most species of Acridiidae not migratory Species ascertained to be 

 migratory Migratory disposition not caused by anatomical dif- 

 ferences : migratory species exist in countries without giving rise 

 to swarms Ravaging power of migratory locusts ; huge size of 

 swarms Famine and pestilence probable sequences No law of 

 periodicity governing destructive flights Phenomenon of migration 

 explained by excessive multiplication Other causes, both imme- 

 diate and remote Remarkable manifestations of instinct attend 

 migration Disappearance of locusts from a spot invaded appa- 

 rently obscure : they again migrate after growth to land of ances- 

 tors " Voetgangers," interesting points in their natural history 

 How these wingless locusts cross rivers Distance to which swarms 



