﻿30 
  THE 
  DISPERSION 
  OF 
  THE 
  GIPSY 
  MOTH. 
  

  

  dying. 
  The 
  tests 
  were 
  carried 
  on 
  under 
  laboratory 
  conditions 
  which 
  

   were 
  unfavorable 
  to 
  the 
  insects. 
  

  

  During 
  the 
  winter 
  of 
  1911-12 
  a 
  few 
  experiments 
  of 
  the 
  same 
  sort 
  

   Avere 
  tried 
  at 
  the 
  gipsy-moth 
  parasite 
  laboratory, 
  and 
  records 
  rang- 
  

   ing 
  from 
  31 
  to 
  138 
  feet 
  have 
  been 
  secured. 
  The 
  conditions 
  for 
  

   making 
  the 
  tests 
  were 
  very 
  unsatisfactory, 
  and 
  it 
  is 
  probable 
  that 
  

   newly 
  hatched 
  larvae, 
  without 
  food, 
  would 
  be 
  able 
  to 
  crawl, 
  on 
  the 
  

   average, 
  about 
  100 
  feet 
  in 
  the 
  open 
  before 
  death 
  would 
  ensue. 
  This 
  

   does 
  not 
  give 
  the 
  maximum 
  distance 
  that 
  the 
  majority 
  of 
  larvae 
  

   could 
  crawl, 
  because 
  many 
  of 
  them 
  in 
  going 
  that 
  distance 
  would 
  find 
  

   some 
  foliage 
  which 
  could 
  be 
  eaten 
  and 
  thus 
  would 
  be 
  enabled 
  to 
  

   proceed 
  farther. 
  

  

  DEGREE 
  OF 
  INFESTATION. 
  

  

  The 
  degree 
  of 
  infestation 
  has 
  an 
  important 
  bearing 
  on 
  dispersion. 
  

   When 
  only 
  a 
  few 
  egg 
  clusters 
  are 
  present 
  on 
  a 
  tree 
  the 
  larvae 
  have 
  

   plenty 
  of 
  food, 
  and 
  it 
  is 
  not 
  necessary 
  for 
  them 
  to 
  move 
  about 
  so 
  

   actively. 
  As 
  the 
  infestation 
  increases 
  the 
  feeding 
  conditions 
  become 
  

   more 
  crowded, 
  and, 
  as 
  a 
  result, 
  the 
  larvae 
  are 
  disturbed 
  and 
  large 
  

   numbers 
  of 
  them 
  spin 
  to 
  the 
  ground. 
  In 
  badly 
  infested 
  places 
  the 
  

   air 
  is 
  sometimes 
  well 
  filled 
  with 
  a 
  network 
  of 
  silken 
  threads, 
  which 
  

   are 
  made 
  by 
  larvae 
  spinning 
  to 
  the 
  ground 
  (PI. 
  XII), 
  and 
  it 
  is 
  

   possible 
  to 
  see 
  large 
  numbers 
  of 
  them 
  hanging 
  from 
  the 
  trees. 
  

  

  These 
  conditions 
  favor 
  dispersion 
  by 
  the 
  wind. 
  

  

  KINDS 
  OF 
  FOOD 
  PLANTS. 
  

  

  At 
  the 
  time 
  the 
  gipsy 
  moth 
  first 
  became 
  noticeable 
  in 
  this 
  country 
  

   and 
  caused 
  so 
  much 
  damage, 
  it 
  seemed 
  almost 
  impossible 
  to 
  find 
  

   plants 
  upon 
  which 
  it 
  would 
  not 
  feed. 
  Many 
  experiments 
  were 
  

   carried 
  on 
  with 
  fifth 
  and 
  sixth 
  stage 
  caterpillars, 
  which 
  Avere 
  fed 
  in 
  

   glass 
  jars 
  upon 
  various 
  kinds 
  of 
  foliage, 
  and 
  very 
  feAV 
  plants 
  Avere 
  

   rejected, 
  especially 
  if 
  the 
  insects 
  Avere 
  supplied 
  Avith 
  no 
  other 
  food. 
  

   The 
  results 
  of 
  these 
  experiments 
  Avere 
  published 
  by 
  Forbush 
  and 
  

   Fernald 
  in 
  1896. 
  Since 
  that 
  time 
  it 
  has 
  become 
  gradually 
  more 
  

   noticeable 
  that 
  the 
  larvae 
  show 
  marked 
  preference 
  for 
  certain 
  species 
  

   of 
  trees. 
  This 
  may 
  be 
  due 
  to 
  a 
  gradual 
  change 
  of 
  habit, 
  or 
  to 
  the 
  

   fact 
  that 
  caterpillars 
  Avhich 
  do 
  not 
  find 
  food 
  Avhich 
  is 
  most 
  suitable, 
  

   although 
  they 
  may 
  strip 
  and 
  injure 
  the 
  tree, 
  may 
  not 
  come 
  through 
  

   to 
  maturity. 
  

  

  There 
  is 
  considerable 
  difference 
  in 
  food 
  requirements 
  of 
  the 
  small 
  

   and 
  the 
  large 
  caterpillars 
  of 
  this 
  insect, 
  the 
  former 
  not 
  being 
  able 
  

   to 
  survive 
  on 
  some 
  species 
  of 
  trees 
  upon 
  which 
  the 
  larger 
  ones 
  Avill 
  

   feed. 
  The 
  Avhite 
  pine 
  is 
  one 
  of 
  the 
  trees 
  of 
  which 
  this 
  may 
  be 
  said, 
  

   and 
  it 
  has 
  been 
  repeatedly 
  demonstrated 
  that 
  the 
  first-stage 
  larA 
  r 
  a> 
  can 
  

  

  