﻿INVADING 
  SWARMS 
  USUALLY 
  COME 
  FROM 
  NORTHWEST. 
  75 
  

  

  1865. 
  — 
  Locusts 
  flew 
  into 
  Minnesota 
  from 
  the 
  west 
  and 
  north 
  

  

  1866. 
  — 
  There 
  was 
  ;i 
  general 
  invasion 
  from 
  the 
  west 
  and 
  northwest, 
  which 
  reached 
  

   to 
  Texa>. 
  

  

  1868. 
  — 
  Locusts 
  appeared 
  in 
  Riley 
  County, 
  Kaus.. 
  from 
  a 
  northerly 
  direction, 
  the 
  

   exact 
  direction 
  not 
  clearly 
  ascertained. 
  

  

  1873. 
  — 
  Locusts 
  entered 
  Texas 
  in 
  September 
  from 
  the 
  north. 
  

  

  1874. 
  — 
  This 
  was 
  a 
  very 
  general 
  invasion, 
  and 
  all 
  accounts 
  show 
  that 
  the 
  flights 
  were 
  

   from 
  the 
  northwest. 
  

  

  l-?r>. 
  — 
  Eagle 
  Pass, 
  Texas, 
  was 
  visited 
  by 
  swarms, 
  moving 
  from 
  the 
  north, 
  in 
  Sep- 
  

   tember. 
  From 
  Dakota 
  the 
  locusts 
  migrated 
  from 
  the 
  middle 
  of 
  July 
  until 
  the 
  middle 
  

   of 
  August, 
  moving 
  south 
  or 
  southeast. 
  But 
  there 
  appears 
  to 
  have 
  been 
  no 
  general 
  

   invasion 
  of 
  the 
  intermediate 
  States 
  and 
  Territories. 
  

  

  T876. 
  — 
  There 
  were 
  fresh 
  arrivals 
  in 
  Texas 
  from 
  the 
  north 
  and 
  northwest. 
  During; 
  

   the 
  same 
  year 
  Missouri. 
  Kansas, 
  Nebraska, 
  and 
  Iowa 
  were 
  visited 
  by 
  heavy 
  swarms, 
  

   always 
  coming 
  from 
  the 
  northwest. 
  

  

  Some 
  of 
  the 
  swarms 
  this 
  season 
  were 
  traced 
  back 
  nearly 
  or 
  quite 
  to 
  the 
  borders 
  of 
  

   Montana, 
  at 
  least 
  to 
  the 
  northwestern 
  portion 
  of 
  Dakota. 
  

  

  This 
  is 
  conclusive 
  as 
  to 
  the 
  direction 
  from 
  which 
  invading 
  swarms 
  

   usually 
  arrive 
  in 
  the 
  temporary 
  region, 
  but 
  before 
  it 
  can 
  be 
  made 
  con- 
  

   clusive 
  of 
  the 
  proposition, 
  and 
  of 
  value 
  in 
  studying 
  the 
  life 
  history 
  of 
  the 
  

   species. 
  it 
  is 
  necessary 
  to 
  eliminate 
  two 
  possible 
  explanations 
  which 
  may 
  

   be 
  given 
  without 
  recourse 
  to 
  the 
  hypothesis 
  advanced. 
  

  

  First. 
  It 
  may 
  be 
  contended, 
  as 
  the 
  writer 
  and 
  Dr. 
  Scudder 
  at 
  one 
  time> 
  

   held, 
  following 
  the 
  idea 
  advanced 
  by 
  Keferstein, 
  Zinnani, 
  Schrank, 
  Kop- 
  

   pen, 
  and 
  some 
  other 
  European 
  entomologists, 
  that 
  these 
  invasions 
  may 
  

   be 
  from 
  points 
  much 
  nearer 
  the 
  place 
  of 
  arrival 
  than 
  generally 
  supposed 
  

   and 
  indicated 
  in 
  the 
  above 
  proposition. 
  For 
  illustration, 
  may 
  not 
  the 
  

   swarms 
  that 
  reach 
  Texas 
  come 
  from 
  Eastern 
  Colorado 
  or 
  Indian 
  Terri- 
  

   tory 
  ; 
  those 
  arriving 
  in 
  Kansas, 
  from 
  Western 
  Nebraska 
  ; 
  those 
  reaching 
  

   Nebraska, 
  from 
  Southwestern 
  Dakota, 
  &c, 
  thus 
  moving 
  on 
  in 
  successive 
  

   waves, 
  each 
  wave 
  representing 
  a 
  generation 
  ? 
  And 
  is 
  it 
  not 
  more 
  than 
  

   likely 
  that 
  the 
  circumstances 
  which 
  cause 
  excessive 
  multiplication 
  at 
  one 
  

   of 
  these 
  points 
  will 
  have 
  the 
  same 
  effect 
  in 
  the 
  other, 
  when 
  these 
  circum- 
  

   stances 
  operate 
  generally 
  over 
  a 
  large 
  area, 
  as 
  in 
  1866, 
  1874, 
  and 
  1876,. 
  

   and 
  hence 
  the 
  movements 
  be 
  apparently 
  the 
  same 
  as 
  if 
  all 
  the 
  swarms 
  

   came 
  from 
  the 
  permanent 
  region 
  of 
  the 
  northwest 
  ! 
  

  

  Secondly. 
  As 
  it 
  has 
  been 
  ascertained 
  that 
  the 
  invading 
  swarms 
  sel- 
  

   dom 
  arrive 
  earlier 
  than 
  July, 
  and 
  often 
  as 
  late 
  as 
  August 
  and 
  the 
  first 
  of 
  

   September, 
  and 
  as 
  those 
  locusts 
  hatched 
  in 
  Texas 
  become 
  full-fledged 
  in 
  

   April 
  and 
  May. 
  those 
  of 
  Kansas 
  in 
  May 
  and 
  June, 
  and 
  those 
  of 
  Xebraska 
  

   in 
  June, 
  and 
  almost 
  universally 
  fly 
  northward 
  soon 
  afterwards, 
  may 
  not 
  

   the 
  invading 
  swarms 
  be 
  the 
  same 
  that 
  moved 
  northward, 
  again 
  return- 
  

   ing 
  southward 
  ! 
  

  

  The 
  second 
  supposition 
  is 
  easily 
  disposed 
  of. 
  That 
  • 
  • 
  returning 
  swarms," 
  

   or 
  swarms 
  flying 
  from 
  the 
  temporary 
  region 
  northwest, 
  toward 
  the 
  per- 
  

   manent 
  area, 
  do 
  often 
  change 
  their 
  course 
  and 
  again 
  move 
  south, 
  and 
  

   are 
  sometimes 
  taken 
  for 
  "invaders," 
  is 
  certainly 
  true, 
  as 
  we 
  know 
  from 
  

   data 
  collected 
  in 
  1877. 
  But 
  this 
  will 
  not 
  apply 
  in 
  years 
  when 
  no 
  swarms. 
  

  

  