﻿BOUNDARY 
  OF 
  PERMANENT 
  REGION. 
  5& 
  

  

  them 
  from 
  A. 
  americanum 
  and 
  agreeing 
  exactly 
  with 
  that 
  of 
  the 
  former 
  

   species. 
  

  

  Mr. 
  E. 
  Flint, 
  in 
  his 
  letter 
  of 
  December 
  18, 
  1877, 
  speaking 
  of 
  the 
  migra- 
  

   tory 
  locusts 
  that 
  visit 
  Nicaragua, 
  says 
  : 
  " 
  They 
  resemble 
  CEdipoda 
  Say 
  * 
  r 
  

   these 
  have 
  spotted 
  elytra 
  wings, 
  and 
  are 
  larger 
  ; 
  last 
  ventral 
  segment 
  

   notched, 
  as 
  in 
  spretus." 
  151 
  

  

  According 
  to 
  his 
  letter 
  specimens 
  were 
  sent 
  to 
  the 
  Smithsonian 
  Insti- 
  

   tution 
  for 
  determination, 
  but 
  we 
  cannot 
  learn 
  that 
  they 
  were 
  ever 
  re- 
  

   ceived.* 
  We 
  think 
  it 
  almost 
  certain 
  that 
  the 
  species 
  does 
  not 
  belong 
  to 
  

   the 
  genus 
  (Edipoda, 
  or 
  to 
  the 
  group 
  (Edipodini. 
  It 
  is 
  most 
  probably 
  an 
  

   Acridium, 
  either 
  A. 
  americanum 
  or 
  a 
  closely 
  allied 
  species; 
  the 
  " 
  spotted 
  

   elytra" 
  and 
  notch 
  in 
  the 
  last 
  ventral 
  segment 
  agree 
  with 
  this 
  supposi- 
  

   tion, 
  the 
  prominent 
  notch 
  in 
  the 
  male 
  of 
  this 
  species 
  being 
  readily 
  ob- 
  

   served. 
  In 
  addition 
  to 
  this 
  we 
  may 
  say 
  that 
  large 
  (Edipodce 
  appear 
  to 
  

   be 
  very 
  rare 
  in 
  Southern 
  Mexico 
  and 
  Central 
  America, 
  while 
  in 
  this 
  re- 
  

   gion 
  and 
  the 
  northern 
  part 
  of 
  South 
  America 
  Acridium 
  reaches 
  the 
  

   maximum 
  in 
  development. 
  A 
  small 
  collection 
  made 
  last 
  summer 
  in 
  

   Central 
  America 
  by 
  Professor 
  Burrill 
  contained 
  but 
  a 
  single 
  (Edipodean. 
  

  

  These 
  reasons, 
  we 
  think, 
  are 
  sufficient 
  to 
  render 
  it 
  more 
  than 
  prob- 
  

   able 
  that 
  the 
  Eocky 
  Mountain 
  locust 
  does 
  not 
  extend 
  its 
  incursions 
  into 
  

   Mexico 
  or 
  Central 
  America. 
  

  

  The 
  line 
  on 
  map 
  No. 
  1, 
  marking 
  the 
  outer 
  limits 
  of 
  its 
  distribution 
  as 
  

   given 
  in 
  our 
  former 
  report, 
  may 
  be 
  considered 
  as 
  very 
  nearly 
  correct^ 
  

   requiring 
  no 
  change, 
  perhaps, 
  except 
  at 
  one 
  point. 
  Facts 
  ascertained 
  

   during 
  the 
  past 
  and 
  present 
  season 
  indicate 
  a 
  more 
  southern 
  extension 
  

   in 
  New 
  Mexico, 
  and 
  possibly 
  in 
  Arizona. 
  We 
  have, 
  then, 
  an 
  area 
  ex- 
  

   tending 
  east 
  and 
  west 
  from 
  the 
  93° 
  to 
  119° 
  of 
  west 
  longitude 
  and 
  north 
  

   and 
  south 
  from 
  27° 
  to 
  53° 
  of 
  north 
  latitude 
  ; 
  or 
  26° 
  east 
  and 
  west 
  and 
  

   26° 
  north 
  and 
  south, 
  which 
  has 
  as 
  its 
  strongly 
  marked 
  features 
  an 
  im- 
  

   mense 
  and 
  highly 
  elevated 
  plateau 
  from 
  which 
  shoot 
  up 
  sharp 
  ranges 
  and 
  

   lofty 
  peaks. 
  This 
  elevated 
  section 
  is 
  bordered 
  by 
  broad, 
  treeless 
  plains 
  ; 
  

   the 
  entire 
  area 
  is 
  to 
  a 
  large 
  extent 
  free 
  from 
  forests, 
  the 
  chief 
  exceptions 
  

   being 
  the 
  higher 
  mountain 
  masses 
  in 
  Colorado 
  and 
  Wyoming, 
  and 
  the 
  

   mountainous 
  section 
  in 
  West 
  Montana. 
  Not 
  only 
  is 
  this 
  vast 
  area, 
  taken 
  

   as 
  a 
  whole, 
  comparatively 
  treeless 
  and 
  barren, 
  but 
  the 
  climate 
  is 
  dry, 
  

   the 
  average 
  rainfall 
  not 
  exceeding 
  twelve 
  or 
  fourteen 
  inches 
  per 
  annum. 
  

  

  By 
  comparing 
  the 
  area 
  of 
  distribution 
  of 
  this 
  species 
  with 
  that 
  of 
  

   other 
  species, 
  we 
  are 
  enabled 
  to 
  deduce 
  some 
  important 
  laws 
  in 
  refer- 
  

   ence 
  to 
  locust 
  distribution, 
  and 
  the 
  laws 
  of 
  migration 
  which 
  cannot 
  be 
  

   detected 
  by 
  studying 
  one 
  species 
  alone. 
  

  

  The 
  paper 
  by 
  Mr. 
  F. 
  T. 
  Koppen 
  in 
  Petermann's 
  " 
  Mittheilungen 
  aus 
  

   Justus 
  Perthes' 
  Geographischer 
  Anstalt," 
  in 
  regard 
  to 
  the 
  distribution 
  

   of 
  Paehytylus 
  migratorius 
  has 
  already 
  been 
  referred 
  to 
  in 
  our 
  former 
  re- 
  

   port, 
  and 
  M. 
  Preudhomme 
  de 
  Borre's 
  brief 
  analysis 
  of 
  it 
  is 
  given 
  there. 
  

   According 
  to 
  this 
  the 
  northern 
  limit 
  of 
  the 
  permanent 
  distribution 
  of 
  

  

  157 
  See 
  former 
  Report, 
  p. 
  465. 
  

  

  *Note. 
  — 
  Specimens, 
  possibly 
  of 
  this 
  collection, 
  sent 
  us 
  are 
  closely 
  allied 
  to 
  A. 
  peregrinum. 
  

  

  