﻿188 
  rRocEEDiyiGS 
  of 
  the 
  xatioxal 
  museum. 
  

  

  South 
  Saskatcbewaii 
  to 
  Wyoming, 
  inclusive, 
  and 
  in 
  the 
  Bocky 
  Moun- 
  

   tain 
  region 
  proper 
  in 
  Colorado 
  and 
  Utah. 
  

  

  (2) 
  In 
  certain 
  years, 
  especially 
  in 
  dry 
  seasons, 
  between 
  mid-July 
  and' 
  

   mid 
  September, 
  migratory 
  hordes 
  of 
  incredible 
  numbers 
  and 
  of 
  both 
  

   sexes 
  pass 
  from 
  their 
  natural 
  breeding 
  grounds 
  to 
  the 
  east, 
  southeast, 
  

   and 
  south, 
  conveyed 
  by 
  the 
  winds 
  (toward 
  which 
  tbey 
  head) 
  over 
  a 
  

   greater 
  or 
  less 
  and 
  sometimes 
  a 
  vast 
  extent 
  of 
  country 
  from 
  Lake 
  Win- 
  

   nipeg 
  to 
  or 
  almost 
  to 
  the 
  Gulf 
  of 
  Mexico, 
  rarely 
  passing 
  farther 
  east 
  

   tban 
  longitude 
  93°, 
  and 
  devastating 
  the 
  countries 
  they 
  reach 
  to 
  an 
  

   alarming 
  extent, 
  sometimes 
  in 
  places 
  absolutely 
  destroying 
  all 
  standing 
  

   crops 
  and 
  defoliating 
  fruit 
  trees. 
  

  

  (3) 
  As 
  they 
  rise 
  for 
  flight 
  from 
  home 
  only 
  in 
  dry 
  clear 
  weather 
  (when 
  

   the 
  prevailing 
  winds 
  are 
  from 
  the 
  north 
  or 
  northwest), 
  they 
  do 
  not 
  seri- 
  

   ously 
  invade 
  the 
  regions 
  (mostly 
  infertile) 
  to 
  the 
  west 
  of 
  their 
  home. 
  

  

  (4) 
  The 
  invaders 
  extend 
  or 
  may 
  extend 
  their 
  flights 
  to 
  a 
  distance 
  ofi 
  

   at 
  least 
  500 
  miles 
  from 
  their 
  point 
  of 
  origin, 
  but 
  there 
  is 
  no 
  clear 
  evi- 
  

   dence 
  to 
  show 
  that 
  (as 
  claimed 
  by 
  the 
  Commission) 
  they 
  extend 
  it 
  to 
  

   double 
  that 
  distance. 
  

  

  (5) 
  They 
  deposit 
  their 
  eggs 
  throughout 
  the 
  invaded 
  territory, 
  but 
  

   their 
  descendants 
  therein 
  of 
  the 
  succeeding 
  year 
  not 
  only 
  do 
  not 
  effect 
  

   a 
  tithe 
  of 
  the 
  damage 
  of 
  the 
  preceding 
  year 
  (although 
  on 
  the 
  ground 
  

   earlier), 
  but 
  when 
  winged 
  move 
  about 
  in 
  swarms 
  from 
  place 
  to 
  place, 
  

   their 
  prevailing 
  direction 
  — 
  at 
  least 
  during 
  the 
  earlier 
  part 
  of 
  tlie 
  sea- 
  

   son 
  — 
  being 
  the 
  reverse 
  of 
  that 
  of 
  their 
  parents; 
  but 
  even 
  when 
  they 
  

   alight 
  and 
  cover 
  the 
  ground 
  they 
  are 
  far 
  less 
  harmful 
  than 
  were 
  their 
  

   invading 
  parents. 
  

  

  (G) 
  With 
  few 
  exceptions, 
  movements 
  on 
  the 
  wing 
  are 
  with 
  or 
  nearly 
  

   with 
  the 
  wind, 
  and 
  are 
  usually 
  made 
  in 
  clear 
  weather 
  between 
  9 
  a. 
  m. 
  

   and 
  4 
  p. 
  m., 
  but 
  they 
  are 
  sometimes 
  certainly 
  made 
  at 
  night. 
  

  

  (7) 
  Eelatively 
  speaking, 
  exceedingly 
  few 
  of 
  the 
  returning 
  swarms 
  

   ever 
  reach 
  the 
  true 
  home 
  of 
  the 
  species. 
  As 
  a 
  rule, 
  they 
  show 
  signs 
  of 
  

   enfeeblement 
  and 
  deposit 
  few 
  eggs 
  in 
  the 
  invaded 
  region, 
  so 
  that 
  their 
  

   descendants 
  on 
  the 
  invaded 
  soil 
  grow 
  less 
  and 
  less 
  numerous, 
  and, 
  in 
  

   eiiect 
  if 
  not 
  in 
  fact, 
  die 
  out 
  in 
  the 
  course 
  of 
  a 
  very 
  few, 
  probably 
  at 
  

   most 
  two 
  or 
  three, 
  years. 
  

  

  ] 
  can 
  add 
  almost 
  nothing 
  to 
  the 
  facts 
  given 
  by 
  the 
  Entomological 
  

   Commission. 
  It 
  may 
  be 
  worth 
  while 
  to 
  state 
  that 
  in 
  1877 
  I 
  took 
  or 
  

   noted 
  tills 
  insect 
  at 
  the 
  following 
  points: 
  July 
  11, 
  between 
  Idaho 
  and 
  

   Georgetown, 
  Colorado, 
  common, 
  both 
  mature 
  and 
  immature: 
  July 
  12-13, 
  

   Georgetown, 
  Colorado, 
  from 
  8,500 
  feet 
  to 
  above 
  timber, 
  mature 
  and 
  

   immature; 
  July 
  16, 
  Argentine 
  Pass, 
  Colorado, 
  13,000 
  feet, 
  in 
  abundance, 
  

   from 
  young 
  just 
  hatched 
  to 
  imagos, 
  and 
  masses 
  of 
  dead 
  imagos 
  under 
  

   stones 
  on 
  the 
  mountain 
  crests; 
  July 
  20, 
  Laramie, 
  Wyoming; 
  July 
  

   21-31, 
  Green 
  River, 
  Wyoming, 
  plenty 
  but 
  not 
  abundant 
  and 
  mostly 
  

   mature; 
  Alkali 
  Station, 
  north 
  of 
  Green 
  River, 
  Wyoming, 
  G,000 
  feet; 
  

   August 
  1-4, 
  Salt 
  Lake 
  Valley, 
  mostly 
  mature, 
  very 
  plenty 
  everywhere 
  

  

  