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  THE 
  DISPERSION 
  OF 
  THE 
  GIPSY 
  MOTH. 
  

  

  On 
  May 
  6 
  a 
  large 
  tray 
  of 
  caterpillars 
  was 
  placed 
  in 
  a 
  room 
  in 
  

   direct 
  sunlight 
  and 
  the 
  temperature 
  rose 
  to 
  100° 
  F. 
  This 
  resulted 
  in 
  

   abnormal 
  activity, 
  and 
  many 
  of 
  the 
  larvae 
  spun 
  a 
  considerable 
  quan- 
  

   tity 
  of 
  silk. 
  

  

  In 
  order 
  to 
  check 
  these 
  experiments, 
  Mr. 
  Collins 
  made 
  a 
  series 
  of 
  

   field 
  observations 
  in 
  woodland 
  in 
  Melrose, 
  Saugus, 
  and 
  Reading. 
  

  

  FIELD 
  OBSERVATIONS. 
  

  

  May 
  13, 
  1911, 
  visited 
  woods 
  east 
  of 
  the 
  laboratory 
  at 
  Melrose 
  Highlands, 
  

   which 
  had 
  been 
  badly 
  infested 
  and 
  partially 
  to 
  wholly 
  defoliated 
  in 
  1909 
  and 
  

   1910. 
  Infestation 
  not 
  as 
  bad 
  this 
  year. 
  At 
  9.30 
  a. 
  m. 
  the 
  temperature 
  in 
  the 
  

   sun 
  was 
  92° 
  F. 
  ; 
  in 
  the 
  shade, 
  84° 
  F. 
  

  

  All 
  eggs 
  have 
  apparently 
  hatched, 
  and 
  the 
  caterpillars 
  are 
  in 
  the 
  first 
  stage. 
  

   There 
  is 
  plenty 
  of 
  foliage. 
  Very 
  little 
  spinning 
  was 
  observed. 
  In 
  the 
  afternoon 
  

   of 
  the 
  same 
  day 
  visited 
  badly 
  infested 
  woods 
  in 
  Saugus. 
  Temperature, 
  96° 
  F. 
  

   in 
  sun; 
  84° 
  F. 
  in 
  shade. 
  A 
  strong 
  wind 
  was 
  blowing, 
  which 
  varied 
  from 
  

   northwest 
  to 
  southwest. 
  First-stage 
  caterpillars 
  were 
  spinning 
  some. 
  If 
  a 
  

   branch 
  was 
  shaken, 
  they 
  would 
  spin 
  down 
  and 
  be 
  blown 
  away. 
  

  

  On 
  the 
  following 
  day 
  observations 
  were 
  made 
  at 
  Reading, 
  Mass. 
  The 
  tem- 
  

   perature 
  ranged 
  from 
  85° 
  F. 
  in 
  the 
  sun 
  to 
  79° 
  F. 
  in 
  the 
  shade; 
  the 
  wind 
  was 
  

   west 
  and 
  southwest, 
  but 
  rather 
  cool. 
  First-stage 
  caterpillars 
  were 
  feeding 
  

   steadily 
  and 
  spinning 
  freely. 
  Twenty 
  very 
  small 
  first-stage 
  larva? 
  and 
  two 
  that 
  

   were 
  nearly 
  ready 
  to 
  molt 
  were 
  observed 
  spinning 
  down 
  from 
  a 
  white-oak 
  tree. 
  

   Threads 
  from 
  2 
  to 
  4 
  feet 
  long 
  were 
  noted, 
  but 
  it 
  was 
  very 
  difficult 
  to 
  determine 
  

   the 
  quantity 
  of 
  silk 
  spun, 
  as 
  it 
  is 
  almost 
  invisible. 
  A 
  considerable 
  quantity 
  

   of 
  silk 
  was 
  noticed 
  among 
  the 
  small 
  twigs 
  and 
  branches 
  on 
  this 
  tree, 
  therefore 
  

   it 
  is 
  evident 
  that 
  frequent 
  spinning 
  had 
  been 
  attempted 
  by 
  the 
  larvae. 
  

  

  Although 
  few 
  7 
  field 
  observations 
  were 
  made 
  to 
  determine 
  the 
  tem- 
  

   perature 
  at 
  which 
  gipsy-moth 
  caterpillars 
  are 
  active, 
  it 
  is 
  evident 
  that 
  

   the 
  results 
  do 
  not 
  vary 
  greatly 
  from 
  those 
  carried 
  on 
  in 
  the 
  labora- 
  

   tory. 
  Experiments 
  show 
  7 
  that 
  there 
  is 
  practically 
  no 
  activity 
  when 
  the 
  

   temperature 
  is 
  below 
  60° 
  F., 
  and 
  that 
  only 
  a 
  part 
  of 
  the 
  caterpillars 
  

   move 
  about 
  at 
  65° 
  F. 
  Above 
  this 
  point 
  activity 
  increases 
  rapidly. 
  

  

  RELATION 
  OF 
  ACTIVITY 
  TO 
  THE 
  SPINNING 
  OF 
  SILK. 
  

  

  The 
  above 
  experiments 
  show 
  that 
  the 
  activity 
  of 
  the 
  caterpillars 
  

   is 
  governed 
  by 
  the 
  temperature, 
  and 
  it 
  is 
  obvious 
  that 
  the 
  spinning 
  

   of 
  silk 
  depends 
  largely 
  upon 
  the 
  activity 
  of 
  the 
  larva?, 
  and 
  hence 
  

   upon 
  the 
  temperature. 
  There 
  are 
  other 
  factors, 
  however, 
  that 
  enter 
  

   into 
  the 
  problem, 
  and 
  these 
  must 
  be 
  considered 
  with 
  the 
  element 
  of 
  

   temperature. 
  They 
  are 
  : 
  

  

  Location 
  where 
  eggs 
  are 
  deposited. 
  

   Degree 
  of 
  infestation. 
  

   Kind 
  of 
  food 
  plants. 
  

  

  Condition 
  of 
  food 
  plants. 
  

  

  Direction 
  and 
  character 
  of 
  the 
  wind. 
  

  

  LOCATIONS 
  WHERE 
  EGG 
  CLUSTERS 
  ARE 
  DEPOSITED. 
  

  

  The 
  egg 
  clusters 
  of 
  the 
  gipsy 
  moth 
  are 
  not 
  always 
  deposited 
  on 
  

   the 
  plant 
  which 
  furnishes 
  the 
  food 
  for 
  the 
  previous 
  generation. 
  In 
  

   fact, 
  when 
  the 
  caterpillars 
  are 
  nearly 
  ready 
  to 
  transform 
  they 
  usually 
  

  

  