﻿HABITS 
  AND 
  PECULIARITIES 
  OF 
  THE 
  ARMY 
  WORM. 
  109 
  

  

  part 
  of 
  their 
  lives 
  the 
  larvse 
  are 
  very 
  similar 
  iu 
  their 
  habits 
  to 
  the 
  many 
  

   species 
  of 
  cut-worms, 
  working 
  upon 
  the 
  leaves 
  of 
  grass 
  or 
  grain 
  during 
  

   the 
  night 
  or 
  iu 
  cloudy 
  weather, 
  and 
  hiding 
  during 
  the 
  bright 
  sunshine. 
  

   The 
  fact 
  cannot 
  be 
  too 
  strongly 
  insisted 
  upon 
  that 
  the 
  traveling 
  of 
  the 
  

   worms 
  in 
  large 
  armies 
  is 
  abnormal. 
  During 
  nearly 
  the 
  whole 
  year, 
  in 
  

   regions 
  subject 
  to 
  their 
  incursions, 
  the 
  worms 
  may 
  be 
  found 
  in 
  grass- 
  

   fields, 
  high 
  or 
  low 
  (perhaps 
  more 
  often 
  in 
  the 
  low 
  lands 
  bordering 
  

   marshes, 
  as 
  thej 
  are 
  here 
  less 
  liable 
  to 
  disturbance), 
  feeding 
  in 
  the 
  nor- 
  

   mal 
  cut- 
  worm 
  manner. 
  If 
  their 
  numbers 
  be 
  small, 
  they 
  may 
  pass 
  tlieir 
  

   entire 
  lives 
  in 
  this 
  manner, 
  for 
  it 
  is 
  onl^?- 
  when 
  so 
  very 
  abundant 
  that 
  

   the 
  food 
  of 
  the 
  vicinity 
  is 
  destroyed 
  that 
  the 
  worms 
  march 
  in 
  search 
  

   of 
  farther 
  supplies. 
  Ordinai'ily 
  one 
  may 
  pass 
  daily 
  through 
  a 
  grass 
  

   plot 
  where 
  they 
  abound, 
  and 
  never 
  suspect 
  their 
  presence 
  until 
  the 
  plot 
  

   begins 
  suddenly 
  to 
  look 
  bare 
  in 
  patches. 
  Thomas, 
  in 
  his 
  First 
  Illinois 
  

   Eeport, 
  states 
  that, 
  although 
  he 
  was 
  particularly 
  looking 
  for 
  the 
  worms 
  

   during 
  June, 
  1875, 
  he 
  never 
  suspected 
  their 
  presence 
  in 
  a 
  constantly 
  

   frequented 
  grass 
  plot 
  behind 
  his 
  house 
  until 
  it 
  was 
  made 
  manifest 
  in 
  

   this 
  way, 
  by 
  which 
  time 
  the 
  worms 
  had 
  disappeared, 
  the 
  abundance 
  of 
  

   their 
  excrement, 
  however, 
  showing 
  well 
  enough 
  that 
  they 
  had 
  been 
  there. 
  

  

  From 
  the 
  fact 
  that 
  the 
  marching 
  is 
  abnormal, 
  it 
  always 
  happens 
  that 
  

   in 
  marching 
  years 
  many 
  farmers 
  insist 
  that 
  the 
  sedentary 
  worms 
  ravag- 
  

   ing 
  their 
  fields 
  are 
  not 
  the 
  true 
  Army 
  Worms, 
  but 
  simply 
  the 
  " 
  ordinary 
  

   out- 
  worms" 
  which 
  they 
  have 
  with 
  them 
  every 
  year. 
  

  

  When 
  young 
  the 
  worms 
  mimic 
  quite 
  closely 
  the 
  plants 
  upon 
  which 
  

   they 
  feed, 
  and 
  this, 
  with 
  the 
  habit 
  of 
  hiding 
  as 
  they 
  do, 
  by 
  day, 
  and 
  

   dropping 
  when 
  disturbed, 
  renders 
  them 
  very 
  difficult 
  of 
  detection. 
  The 
  

   lighter 
  color 
  of 
  the 
  younger 
  worms 
  found 
  thus 
  concealed 
  has 
  given 
  rise 
  

   to 
  the 
  theory, 
  put 
  forth 
  by 
  Thomas 
  and 
  others, 
  that 
  the 
  marching 
  worms 
  

   belong 
  to 
  a 
  distinct 
  race 
  of 
  the 
  species; 
  but 
  there 
  is 
  not 
  a 
  particle 
  of 
  

   reason 
  in 
  such 
  a 
  theory, 
  for 
  the 
  worms 
  of 
  the 
  marching 
  bodies 
  possessed 
  

   the 
  same 
  light 
  color 
  originally, 
  and 
  indeed 
  the 
  variation 
  is 
  such 
  that 
  

   the 
  same 
  color 
  frequently 
  persists 
  with 
  the 
  full-grown 
  worms, 
  whether 
  

   of 
  the 
  marching 
  bodies 
  or 
  of 
  the 
  normal, 
  hidden 
  individuals. 
  The 
  deep 
  

   color 
  is 
  largely 
  the 
  result 
  of 
  exposure, 
  and 
  whether 
  the 
  sedentary 
  or 
  

   marching 
  habit 
  predominates 
  depends 
  entirely 
  upon 
  circumstances. 
  

  

  Duration 
  of 
  worm 
  life. 
  — 
  With 
  so 
  wide-spread 
  an 
  insect 
  as 
  the 
  

   Army 
  Worm 
  it 
  is 
  impossible 
  to 
  make 
  any 
  general 
  statement 
  concerning 
  

   the 
  duration 
  of 
  any 
  one 
  stage 
  which 
  will 
  hold 
  good. 
  In 
  Saint 
  Louis, 
  in 
  

   the 
  vivarium, 
  at 
  an 
  average 
  temperature 
  of 
  80^ 
  F., 
  we 
  found 
  that 
  cer- 
  

   tain 
  of 
  the 
  worms 
  passed 
  through 
  their 
  five 
  molts 
  at 
  intervals 
  of 
  three 
  

   days, 
  making 
  the 
  entire 
  length 
  of 
  the 
  larval 
  life 
  fifteen 
  or 
  sixteen 
  days. 
  

   The 
  development, 
  however, 
  even 
  of 
  those 
  hatching 
  at 
  the 
  same 
  time 
  from 
  

   the 
  same 
  brood 
  of 
  eggs, 
  is 
  quite 
  irregular 
  and 
  may 
  occupy 
  several 
  days 
  

   longer. 
  In 
  northern 
  Illinois 
  Walsh 
  gives 
  the 
  period 
  at 
  '' 
  from 
  four 
  to 
  

   five 
  weeks," 
  while 
  the 
  shortest 
  period 
  of 
  larval 
  life 
  that 
  Thomas 
  has 
  ob- 
  

   served 
  is 
  twenty-eight 
  days. 
  Individuals 
  reared 
  at 
  the 
  Department 
  of 
  

  

  