CONTENTS. xiii 



SALTATORIA. 

 CHAPTER y. 



LOCUSTS AND (JRASSHclPI'F.RS (aCRIDIID^). 



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

 hopper applied — Acridiidai, prominent characteristics — Anatomy — 

 Organs of special sense — Air-sacs — Acridiida; 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 llight — 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 Acridiid;^ — Change of colour in course of development ... 8i 



CHAPTER \'I. 

 LOCUSTS AND GRASSHOPPKRS (aCRIDI ID.t) — COUtilUli'd. 



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 



