﻿204 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  Stubble, 
  and 
  even 
  under 
  the 
  bark 
  of 
  adjacent 
  posts 
  for 
  the 
  first 
  few 
  days, 
  

   or 
  they 
  may 
  simply 
  rest 
  at 
  full 
  length 
  along 
  a 
  well-shaded 
  leaf. 
  Their 
  

   habit 
  of 
  dropping 
  upon 
  the 
  slightest 
  disturbance, 
  renders 
  their 
  detection 
  

   more 
  difficult. 
  During 
  their 
  first 
  week, 
  they 
  eat 
  only 
  of 
  the 
  lower 
  

   epidermis 
  of 
  the 
  leaf 
  in 
  a 
  manner 
  similar 
  to 
  young 
  Crambid 
  larvae 
  — 
  at 
  

   least 
  such 
  was 
  the 
  habit 
  of 
  those 
  reared 
  the 
  past 
  season. 
  In 
  about 
  a 
  

   week 
  they 
  begin 
  to 
  eat 
  holes 
  in 
  the 
  sides 
  of 
  the 
  leaves, 
  and 
  thereafter 
  

   their 
  appetites 
  develop 
  rapidly. 
  There 
  is 
  considerable 
  difference 
  in 
  the 
  

   growth 
  of 
  the 
  larvae 
  even 
  from 
  the 
  same 
  mass 
  of 
  eggs 
  and 
  under 
  almost 
  

   identical 
  conditions, 
  some 
  being 
  nearly 
  a 
  molt 
  in 
  advance 
  of 
  the 
  others. 
  

   This 
  same 
  difference 
  is 
  the 
  more 
  marked 
  in 
  caterpillars 
  growing 
  under 
  

   natural 
  conditions 
  in 
  the 
  field, 
  where 
  variation 
  is 
  the 
  rule 
  and 
  not 
  the 
  

   exception. 
  The 
  abundance 
  and 
  the 
  condition 
  of 
  the 
  food 
  has 
  a 
  great 
  

   influence 
  on 
  the 
  rapidity 
  of 
  their 
  growth, 
  for 
  if 
  abundant 
  and 
  succulent 
  

   it 
  will 
  be 
  most 
  rapid, 
  while 
  if 
  dry 
  it 
  will 
  be 
  much 
  slower. 
  The 
  parent 
  

   moth 
  apparently 
  seeks 
  to 
  give 
  her 
  offspring 
  the 
  best 
  conditions 
  when 
  she 
  

   searches 
  out 
  the 
  thickest 
  and 
  greenest 
  herbage 
  in 
  which 
  to 
  place 
  her 
  

   eggs, 
  and 
  in 
  most 
  cases 
  it 
  is 
  in 
  just 
  such 
  spots 
  that 
  the 
  destructive 
  

   armies 
  have 
  their 
  origin. 
  They 
  are 
  really 
  centers 
  of 
  distribution, 
  and 
  

   should 
  be 
  so 
  regarded. 
  

  

  Migrations. 
  — 
  The 
  earlier 
  stages 
  of 
  the 
  army-worm 
  escape 
  observation 
  

   in 
  most 
  instances, 
  and 
  it 
  is 
  only 
  when 
  they 
  are 
  unusually 
  abundant 
  and 
  

   after 
  they 
  have 
  become 
  half-grown 
  that 
  they 
  attract 
  attention. 
  It 
  is 
  not 
  

   until 
  then, 
  and 
  after 
  all 
  the 
  food 
  has 
  been 
  devoured 
  in 
  their 
  immediate 
  

   vicinity, 
  that 
  they 
  are 
  noticed. 
  The 
  caterpillars 
  are 
  now 
  forced 
  to 
  move 
  

   elsewhere 
  or 
  starve. 
  In 
  ordinary 
  years 
  this 
  rarely 
  occurs, 
  for 
  they 
  

   are 
  not 
  sufficiently 
  abundant 
  to 
  work 
  any 
  serious 
  injury, 
  unless 
  it 
  be 
  

   a 
  slight 
  thinning 
  of 
  the 
  crop. 
  It 
  will 
  be 
  seen, 
  therefore, 
  that 
  the 
  

   '' 
  marching" 
  habit 
  is 
  abnormal, 
  although 
  it 
  may 
  be 
  the 
  one 
  most 
  familiar 
  

   to 
  many. 
  The 
  uniform 
  movement 
  of 
  the 
  caterpillars 
  in 
  the 
  same 
  direc- 
  

   tion 
  may 
  be 
  explained 
  as 
  the 
  most 
  natural, 
  because 
  it 
  is 
  the 
  easiest 
  when 
  

   they 
  are 
  abundant, 
  for 
  otherwise 
  their 
  opposing 
  motions 
  would 
  be 
  a 
  

   hindrance 
  to 
  one 
  another. 
  The 
  determination 
  of 
  the 
  direction 
  of 
  the 
  

   march 
  is 
  probably 
  the 
  result 
  of 
  chance 
  to 
  a 
  great 
  extent, 
  and 
  is 
  governed 
  

   largely 
  by 
  the 
  direction 
  taken 
  by 
  the 
  first 
  to 
  move, 
  although 
  some 
  are 
  in- 
  

   clined 
  to 
  think 
  that 
  the 
  insects 
  march 
  more 
  frequently 
  toward 
  a 
  certain 
  

   point 
  of 
  the 
  compass, 
  and 
  others 
  beheve 
  that 
  they 
  scent 
  a 
  favorite 
  crop 
  

   in 
  the 
  distance. 
  The 
  food 
  of 
  the 
  caterpillars 
  is 
  so 
  abundant 
  that 
  it 
  hardly 
  

   seems 
  necessary 
  to 
  suppose 
  that 
  they 
  are 
  guided 
  to 
  it 
  by 
  a 
  special 
  

   sense, 
  and 
  it 
  is 
  equally 
  difficult 
  to 
  see 
  how 
  a 
  knowledge 
  of 
  the 
  points 
  of 
  

   the 
  compass 
  would 
  aid 
  materially 
  in 
  such 
  a 
  search. 
  

  

  