﻿16 
  THE 
  DISPERSION 
  OF 
  THE 
  GIPSY 
  MOTH. 
  

  

  colonies 
  which 
  are 
  found 
  long 
  distances 
  from 
  any 
  badly 
  infested 
  area. 
  

   Isolated 
  colonies 
  have 
  been 
  usually 
  so 
  far 
  away 
  from 
  infestations 
  that 
  

   it 
  would 
  have 
  been 
  practically 
  impossible 
  for 
  small 
  females 
  to 
  have 
  

   covered 
  the 
  distance 
  by 
  flying. 
  

  

  SUGGESTIONS 
  CONCERNING 
  THE 
  SPREAD 
  OF 
  LARViE 
  BY 
  THE 
  

  

  WIND. 
  

  

  In 
  the 
  fall 
  of 
  x 
  1909 
  Prof. 
  E. 
  D. 
  Sanderson, 
  who 
  was 
  then 
  ento- 
  

   mologist 
  to 
  the 
  New 
  Hampshire 
  Agricultural 
  Experiment 
  Station, 
  

   and 
  who 
  was 
  deeply 
  interested 
  in 
  the 
  work 
  of 
  suppressing 
  the 
  gipsy 
  

   moth, 
  suggested 
  that 
  the 
  caterpillars 
  of 
  this 
  insect 
  might 
  be 
  car- 
  

   ried 
  by 
  natural 
  means, 
  and 
  later 
  he 
  wrote 
  to 
  Dr. 
  L. 
  O. 
  Howard, 
  

   Chief 
  of 
  the 
  Bureau 
  of 
  Entomology, 
  calling 
  attention 
  to 
  an 
  article 
  

   in 
  the 
  Standard 
  Natural 
  History 
  relative 
  to 
  the 
  peculiar 
  hairs 
  on 
  

   the 
  young 
  caterpillars 
  and 
  suggesting 
  that 
  they 
  might 
  assist 
  the 
  

   larvae 
  in 
  being 
  carried 
  by 
  the 
  wind. 
  An 
  examination 
  of 
  the 
  liter- 
  

   ature 
  showed 
  that 
  the 
  matter 
  had 
  been 
  mentioned 
  by 
  Forbush 
  and 
  

   Fernald 
  in 
  1896 
  and 
  that 
  the 
  hairs 
  had 
  been 
  described 
  by 
  Wachtl 
  

   and 
  Kornauth 
  in 
  a 
  publication 
  relating 
  to 
  experiments 
  in 
  the 
  forests 
  

   of 
  Austria 
  in 
  1893. 
  This 
  paper 
  deals 
  principally 
  with 
  hairs 
  of 
  

   peculiar 
  structure 
  which 
  are 
  found 
  in 
  the 
  first-stage 
  larvae 
  of 
  the 
  

   nun 
  moth 
  {Psilura 
  monacha 
  L.) 
  and 
  states 
  that 
  similar 
  hairs 
  are 
  

   found 
  on 
  the 
  first-stage 
  larvae 
  of 
  Porthetria 
  dispar. 
  

  

  These 
  hairs 
  are 
  not 
  present 
  on 
  the 
  caterpillars 
  in 
  the 
  later 
  stages, 
  

   and 
  as 
  they 
  are 
  provided 
  near 
  the 
  base 
  with 
  a 
  globular 
  enlargement, 
  

   which 
  the 
  authors 
  believed 
  to 
  be 
  filled 
  with 
  air 
  or 
  gas, 
  they 
  were 
  

   called 
  aerostatic 
  hairs 
  and 
  the 
  globes 
  aerophores. 
  They 
  state 
  that 
  

   the 
  first-stage 
  nun 
  larvae 
  are 
  carried 
  long 
  distances 
  by 
  the 
  wind, 
  

   and 
  one 
  might 
  assume 
  that 
  the 
  same 
  is 
  true 
  of 
  the 
  gipsy-moth 
  larvae, 
  

   as 
  they 
  are 
  provided 
  with 
  similar 
  hairs. 
  

  

  A 
  microscopic 
  examination 
  of 
  one 
  of 
  these 
  first-stage 
  caterpillars 
  

   shows 
  that 
  two 
  kinds 
  of 
  hairs 
  arise 
  from 
  the 
  tubercles 
  which 
  are 
  

   arranged 
  in 
  rows 
  on 
  the 
  body. 
  Only 
  a 
  few 
  slender 
  acuminate 
  hairs, 
  

   some 
  of 
  which 
  are 
  nearly 
  half 
  as 
  long 
  as 
  the 
  caterpillar, 
  arise 
  from 
  

   each 
  tubercle 
  (PL 
  V), 
  but 
  many 
  short 
  hairs 
  are 
  present 
  which 
  have 
  

   a 
  small 
  globular 
  swelling 
  near 
  the 
  base. 
  Whether 
  these 
  aerophores 
  

   actually 
  aid 
  in 
  making 
  the 
  caterpillars 
  more 
  buoyant, 
  as 
  is 
  sug- 
  

   gested 
  by 
  the 
  authors 
  above 
  mentioned, 
  is 
  not 
  positively 
  known, 
  

   but 
  it 
  was 
  of 
  great 
  importance 
  to 
  know 
  whether 
  dispersion 
  is 
  actually 
  

   brought 
  about 
  by 
  means 
  of 
  the 
  small 
  larvae 
  drifting 
  in 
  the 
  wind. 
  

  

  EXPERIMENTAL 
  WORK. 
  

  

  In 
  the 
  spring 
  of 
  1910 
  a 
  preliminary 
  experiment 
  was 
  tried 
  in 
  the 
  

   laboratory 
  by 
  releasing 
  caterpillars, 
  which 
  had 
  been 
  encouraged 
  to 
  

   spin 
  as 
  much 
  silk 
  as 
  possible, 
  in 
  front 
  of 
  an 
  electric 
  fan. 
  Although 
  

  

  