﻿32 
  REPORT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

  

  characteristics 
  or 
  differences 
  of 
  sufficient 
  importance 
  to 
  mark 
  the 
  groups 
  

   of 
  the 
  family. 
  If 
  we 
  examine 
  the 
  species 
  of 
  the 
  different 
  restricted 
  gen- 
  

   era 
  containing 
  the 
  more 
  noted 
  locusts, 
  as 
  Pachytylus 
  migratorius, 
  Acrid- 
  

   ium 
  peregrinum, 
  Caloptenus 
  italicus, 
  and 
  Caloptenus 
  spretus, 
  not 
  only 
  do 
  

   we 
  find 
  the 
  same 
  thing 
  true 
  in 
  reference 
  to 
  them, 
  but 
  also 
  that 
  in 
  some 
  

   cases 
  the 
  most 
  closely 
  allied 
  present 
  the 
  strange 
  fact 
  that 
  one 
  is 
  truly 
  

   migratory 
  while 
  the 
  other 
  is 
  not 
  ; 
  as, 
  for 
  example, 
  Caloptenus 
  spretus 
  and 
  

   Caloptenus 
  femur-rubrum 
  of 
  our 
  own 
  country, 
  and 
  Acridium 
  peregrinum 
  

   of 
  the 
  eastern 
  continent, 
  which 
  is 
  scarcely 
  distinguished 
  from 
  Acridium 
  

   americanum 
  of 
  North 
  America. 
  It 
  is 
  therefore 
  evident 
  that 
  we 
  must 
  

   look 
  to 
  something 
  else 
  than 
  such 
  anatomical 
  differences 
  as 
  distinguish 
  

   genera 
  for 
  the 
  cause 
  of 
  the 
  migratory 
  disposition. 
  Before 
  entering 
  upon 
  

   the 
  discussion 
  of 
  this 
  peculiarity 
  in 
  habits, 
  we 
  will 
  first 
  discuss 
  the 
  facts, 
  

   so 
  far 
  as 
  known, 
  in 
  regard 
  to 
  their 
  migrations, 
  with 
  reference 
  chiefly 
  to 
  

   the 
  Eocky 
  Mountain 
  locust 
  of 
  our 
  own 
  country, 
  but 
  referring 
  to 
  other 
  

   species 
  for 
  illustration 
  and 
  to 
  correct 
  what 
  we 
  conceive 
  to 
  be 
  erroneous 
  

   opinions. 
  

  

  In 
  our 
  investigations 
  of 
  the 
  migrations 
  of 
  the 
  Eocky 
  Mountain 
  locust 
  

   we 
  have 
  found 
  it 
  necessary 
  to 
  direct 
  our 
  attention 
  to 
  the 
  following 
  points 
  

   as 
  the 
  ones 
  of 
  chief 
  importance, 
  and 
  as 
  forming 
  the 
  principal 
  divisions 
  

   of 
  the 
  subject 
  : 
  

  

  1. 
  Native 
  breeding 
  ground 
  or 
  point 
  of 
  departure, 
  its 
  position, 
  bound- 
  

   aries, 
  physical 
  features, 
  climate, 
  &c. 
  

  

  2. 
  Habits 
  or 
  characteristics 
  of 
  the 
  species 
  within 
  this 
  area 
  of 
  perma- 
  

   nent 
  distribution, 
  so 
  far 
  as 
  these 
  relate 
  to 
  their 
  movements 
  ; 
  especially 
  the 
  

   question 
  as 
  to 
  whether 
  they 
  are 
  essentially 
  nomadic 
  or 
  sedentary. 
  

  

  3. 
  Their 
  flights. 
  

  

  4. 
  Climatic 
  conditions. 
  

  

  5. 
  Causes 
  of 
  migration. 
  

  

  6. 
  The 
  effect 
  or 
  consequences 
  of 
  these 
  migrations. 
  

  

  The 
  present 
  chapter 
  will 
  be 
  limited 
  strictly 
  to 
  a 
  consideration 
  of 
  the 
  

   "philosophy 
  of 
  migrations," 
  the 
  last 
  and 
  all 
  important 
  topic 
  — 
  "conse- 
  

   quences 
  " 
  — 
  to 
  which 
  the 
  attention 
  of 
  the 
  Commission 
  has 
  been 
  largely 
  

   devoted, 
  being 
  treated 
  of 
  in 
  other 
  chapters. 
  

  

  I. 
  — 
  A 
  BRIEF 
  ACCOUNT 
  OF 
  LOCUST 
  MOVEMENTS 
  IN 
  OTHER 
  COUNTRIES. 
  

  

  As 
  we 
  shall 
  have 
  frequent 
  occasion 
  to 
  refer 
  to 
  the 
  migrations 
  of 
  locusts 
  

   in 
  other 
  countries 
  as 
  well 
  as 
  our 
  own, 
  we 
  will 
  give 
  a 
  brief 
  general 
  review 
  

   of 
  locust 
  movements 
  in 
  various 
  parts 
  of 
  the 
  world, 
  limiting 
  ourselves 
  

   strictly 
  to 
  such 
  facts 
  as 
  have 
  a 
  direct 
  bearing 
  upon 
  the 
  question 
  under 
  

   discussion. 
  For 
  the 
  facts 
  mentioned 
  in 
  this 
  part 
  of 
  the 
  chapter 
  we 
  are 
  

   largely 
  indebted 
  to 
  the 
  following 
  writers, 
  but 
  have 
  endeavored, 
  by 
  a 
  la- 
  

   borious 
  consultation 
  of 
  the 
  authorities 
  quoted, 
  so 
  far 
  as 
  to 
  be 
  found 
  in 
  

   the 
  Congressional 
  and 
  other 
  libraries 
  of 
  our 
  country, 
  to 
  verify 
  these 
  

   quotations 
  : 
  

  

  K. 
  Eitter. 
  — 
  "Die 
  Heuschreokenplage 
  der 
  Lander 
  der 
  Alten 
  Welt,. 
  

  

  