﻿68 
  EEPORT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

  

  district, 
  across 
  the 
  boundaries 
  of 
  which 
  it 
  may 
  and 
  often 
  does 
  extend 
  

   its 
  migrations 
  into 
  other 
  regions, 
  but 
  not 
  to 
  become 
  naturalized 
  therein. 
  

  

  We 
  are 
  fully 
  aware 
  that 
  entomologists 
  describe 
  or 
  note 
  specimens, 
  for 
  

   example, 
  of 
  P. 
  migratorius 
  from 
  numerous 
  points 
  immensely 
  distant 
  

   from 
  the 
  boundaries 
  we 
  have 
  assigned 
  it 
  ; 
  but 
  our 
  experience 
  in 
  refer- 
  

   ence 
  to 
  C. 
  spretus 
  has 
  convinced 
  us 
  that 
  unless 
  such 
  specimens 
  are 
  

   known 
  to 
  have 
  been 
  from 
  migrating 
  hordes 
  the 
  evidence 
  is 
  of 
  but 
  little 
  

   value 
  in 
  determining 
  the 
  question 
  at 
  issue. 
  We 
  freely 
  confess 
  the 
  diffi- 
  

   culty 
  this 
  fact 
  introduces 
  in 
  the 
  attempt 
  to 
  solve 
  the 
  problem 
  $ 
  but 
  whea 
  

   we 
  take 
  into 
  consideration 
  the 
  additional 
  fact 
  of 
  the 
  difficulty 
  of 
  dis- 
  

   tinguishing 
  such 
  closely 
  allied 
  species 
  as 
  C. 
  spretus 
  and 
  C. 
  atlantis 
  with- 
  

   out 
  a 
  careful 
  study 
  of 
  their 
  habits, 
  we 
  can 
  find 
  at 
  least 
  one 
  probable 
  

   explanation. 
  

  

  From 
  the 
  evidence 
  adduced 
  and 
  from 
  our 
  knowledge 
  of 
  our 
  native 
  

   locust, 
  we 
  conclude 
  that 
  each 
  migratory 
  species 
  has 
  its 
  proper 
  native 
  

   habitat 
  or 
  permanent 
  breeding 
  ground, 
  to 
  which, 
  whenever 
  sufficient 
  

   data 
  are 
  obtained, 
  approximate 
  boundaries 
  may 
  be 
  assigned, 
  but 
  that 
  

   as 
  a 
  general 
  rule, 
  to 
  which 
  we 
  know 
  of 
  but 
  one 
  or 
  two 
  exceptions, 
  they 
  

   are 
  essentially 
  migratory 
  within 
  their 
  respective 
  regions 
  of 
  permanent 
  

   distribution. 
  The 
  exceptions 
  alluded 
  to 
  are 
  A, 
  americanum, 
  which 
  is 
  not 
  

   migratory 
  in 
  the 
  United 
  States, 
  but 
  is 
  in 
  the 
  tropical 
  regions, 
  as 
  before 
  

   stated, 
  and 
  P. 
  cinerascens, 
  which 
  is 
  sedentary 
  in 
  parts 
  of 
  Europe 
  at 
  least, 
  

   and 
  also 
  in 
  some 
  other 
  sections. 
  It 
  is 
  possible 
  this 
  is 
  true 
  in 
  reference 
  

   to 
  some 
  other 
  migratory 
  species, 
  but 
  if 
  so 
  we 
  have 
  no 
  evidence 
  of 
  the 
  

   fact 
  ; 
  and, 
  so 
  far 
  as 
  our 
  investigations 
  show, 
  is 
  not 
  true 
  of 
  C. 
  spretus. 
  

   That 
  these 
  permanent 
  areas 
  have 
  expanded 
  in 
  the 
  course 
  of 
  time 
  from 
  

   smaller 
  areas 
  to 
  their 
  present 
  dimensions 
  we 
  think 
  quite 
  certain, 
  but 
  we 
  

   will 
  call 
  attention 
  to 
  this 
  hereafter. 
  

  

  CHARACTER 
  OF 
  THE 
  PERMANENT 
  BREEDING-GROUNDS. 
  

  

  That 
  locusts 
  prefer 
  comparatively 
  barren 
  regions, 
  or 
  at 
  least 
  sections 
  

   free 
  from 
  arboreal 
  and 
  rank 
  vegetation, 
  has 
  already 
  been 
  affirmed. 
  As 
  

   preliminary 
  to 
  our 
  remarks 
  on 
  this 
  point, 
  we 
  call 
  attention 
  to 
  the 
  fol- 
  

   lowing 
  passage 
  in 
  one 
  of 
  Humboldt's 
  works 
  : 
  170 
  

  

  The 
  different 
  quarters 
  of 
  the 
  world 
  have 
  been 
  supposed 
  to 
  be 
  characterized 
  by 
  the 
  

   remark 
  that 
  Europe 
  has 
  its 
  heaths, 
  Asia 
  its 
  steppes, 
  Africa 
  its 
  deserts, 
  and 
  America 
  its 
  

   savannas; 
  but 
  by 
  this 
  distinction 
  contrasts 
  are 
  established 
  that 
  are 
  not 
  founded 
  either 
  

   on 
  the 
  nature 
  of 
  things 
  or 
  the 
  genius 
  of 
  languages. 
  The 
  existence 
  of 
  a 
  heath 
  always 
  

   supposes 
  an 
  association 
  of 
  plants 
  of 
  the 
  family 
  Ericas 
  ; 
  the 
  steppes 
  of 
  Asia 
  are 
  not 
  

   everywhere 
  covered 
  with 
  saline 
  plants 
  ; 
  the 
  savannas 
  of 
  Venezuela 
  furnish 
  not 
  only 
  

   the 
  graminae, 
  but 
  with 
  them 
  small 
  herbaceous 
  mimosa, 
  legumina, 
  and 
  other 
  dicoty- 
  

   ledonous 
  plants. 
  The 
  plains 
  of 
  Songaria, 
  those 
  which 
  extend 
  between 
  the 
  Don 
  and 
  

   Volga, 
  and 
  the 
  puszta 
  of 
  Hungary 
  are 
  real 
  savannas, 
  pasturages 
  abounding 
  in 
  grasses 
  \ 
  

   while 
  the 
  savannas 
  to 
  the 
  east 
  and 
  west 
  of 
  the 
  Rocky 
  Mountains 
  and 
  of 
  New 
  Mexico- 
  

   produce 
  Chenopodiums 
  containing 
  carbonate 
  and 
  muriate 
  of 
  soda. 
  Asia 
  has 
  real 
  

   deserts 
  destitute 
  of 
  vegetation 
  in 
  Arabia, 
  Gobi, 
  and 
  in 
  Persia. 
  Since 
  we 
  have 
  bo- 
  

   rn 
  Personal 
  Narrative 
  of 
  a 
  Journey 
  to 
  the 
  Equinoctial 
  Regions 
  of 
  the 
  New 
  Continent. 
  Bohn'e 
  ed., 
  

   1852, 
  vol. 
  ii, 
  p. 
  85. 
  

  

  