﻿22 
  

  

  THE 
  DISPERSION 
  OF 
  THE 
  GIPSY 
  MOTH. 
  

  

  very 
  active 
  unless 
  the 
  weather 
  is 
  warm, 
  and 
  when 
  the 
  experiments 
  

   were 
  conducted 
  on 
  cool 
  days 
  it 
  was 
  necessary 
  to 
  strike 
  the 
  box 
  in 
  

   which 
  the 
  egg 
  clusters 
  and 
  caterpillars 
  were 
  confined 
  in 
  order 
  to 
  jar 
  

   more 
  of 
  the 
  larvae 
  from 
  the 
  open 
  end 
  and 
  induce 
  them 
  to 
  spin 
  down 
  

   toward 
  the 
  ground. 
  If 
  a 
  strong 
  wind 
  was 
  blowing 
  at 
  the 
  time, 
  they 
  

   would 
  be 
  caught 
  up 
  and 
  blown 
  away, 
  and 
  occasionally 
  it 
  was 
  possible 
  

   to 
  see 
  them 
  drift 
  20 
  or 
  30 
  feet 
  before 
  they 
  passed 
  from 
  view. 
  Table 
  

   I 
  gives 
  a 
  summary 
  of 
  the 
  data 
  secured 
  in 
  these 
  experiments. 
  

  

  Table 
  I. 
  — 
  Direction 
  and 
  velocity 
  of 
  wind, 
  at 
  Lynn 
  Marshes, 
  Mass. 
  

  

  to 
  12, 
  1910. 
  

  

  May 
  6 
  

  

  Date. 
  

  

  Screens 
  

  

  Wind. 
  

  

  Average 
  

  

  

  

  

  

  No 
  

  

  Distance 
  

  

  Direc- 
  

  

  Average 
  

  

  tem- 
  

   perature. 
  

  

  

  station. 
  

  

  tion. 
  

  

  velocity. 
  

  

  

  

  

  

  Miles 
  

  

  

  

  Feel. 
  

  

  

  ■per 
  hour. 
  

  

  °F. 
  

  

  1 
  

  

  50 
  

  

  NW. 
  

  

  11 
  

  

  60 
  

  

  1 
  

  

  100 
  

  

  NW. 
  

  

  11 
  

  

  61 
  

  

  3 
  

  

  150 
  

  

  sw. 
  

  

  14 
  to 
  17 
  

  

  66 
  to 
  70 
  

  

  3 
  

  

  200 
  

  

  sw. 
  

  

  14 
  to 
  17 
  

  

  66 
  to 
  70 
  

  

  3 
  

  

  250 
  

  

  sw. 
  

  

  14 
  to 
  17 
  

  

  66 
  to 
  70 
  

  

  3 
  

  

  300 
  

  

  sw. 
  

  

  14 
  to 
  17 
  

  

  66 
  to 
  70 
  

  

  3 
  

  

  350 
  

  

  sw. 
  

  

  18 
  to 
  23 
  

  

  63 
  to 
  67 
  

  

  3 
  

  

  500 
  

  

  sw. 
  

  

  15 
  

  

  63 
  

  

  3 
  

  

  600 
  

  

  sw. 
  

  

  15 
  

  

  66 
  

  

  ? 
  

  

  700 
  

   1.833 
  

  

  w. 
  

   w. 
  

  

  

  

  1 
  

  

  7 
  to 
  19 
  

  

  51 
  to 
  66 
  

  

  Number 
  

   of 
  larvae 
  

   caught. 
  

  

  1910. 
  

   May 
  6 
  

  

  Do 
  

  

  May 
  7 
  

  

  Do 
  

  

  Do 
  

  

  Do 
  

  

  Mav 
  10 
  

  

  May 
  11 
  

  

  Do 
  

  

  May 
  12 
  

  

  Do 
  

  

  The 
  temperature 
  records 
  and 
  velocity 
  of 
  the 
  winds 
  were 
  secured 
  

   through 
  the 
  courtesy 
  of 
  the 
  United 
  States 
  Weather 
  Bureau 
  at 
  Boston. 
  

  

  The 
  notes 
  that 
  were 
  kept 
  on 
  the 
  marshes 
  show 
  that 
  the 
  direction 
  

   of 
  the 
  wind 
  varied 
  slightly 
  from- 
  the 
  Weather 
  Bureau 
  records, 
  and 
  

   the 
  former 
  are 
  given 
  above. 
  In 
  'other 
  respects 
  there 
  were 
  probably 
  

   minor 
  differences, 
  but 
  they 
  would 
  not 
  affect 
  the 
  result 
  to 
  any 
  great 
  

   extent. 
  It 
  should 
  be 
  noted, 
  however, 
  that 
  on 
  none 
  of 
  the 
  days 
  men- 
  

   tioned 
  did 
  the 
  wind 
  maintain 
  a 
  velocity 
  which 
  was 
  at 
  all 
  constant, 
  

   and 
  changes 
  in 
  direction 
  were 
  sudden 
  and 
  variable. 
  This 
  added 
  to 
  

   the 
  difficulty 
  in 
  carrying 
  on 
  the 
  experiments 
  and 
  made 
  it 
  necessary 
  

   to 
  change 
  repeatedly 
  the 
  location 
  of 
  the 
  screens. 
  The 
  most 
  data 
  

   were 
  secured 
  on 
  May 
  7, 
  and, 
  by 
  referring 
  to 
  the 
  table, 
  it 
  will 
  be 
  noted 
  

   that 
  the 
  weather 
  was 
  warmer 
  than 
  on 
  any 
  of 
  the 
  other 
  days 
  when 
  

   tests 
  were 
  made 
  ; 
  also 
  the 
  direction 
  of 
  the 
  wind 
  was 
  more 
  constant. 
  

  

  These 
  experiments 
  indicate 
  that 
  the 
  best 
  opportunity 
  for 
  the 
  dis- 
  

   persion 
  of 
  gipsy-moth 
  caterpillars 
  by 
  the 
  wind 
  is 
  when 
  the 
  tempera- 
  

   ture 
  is 
  above 
  65° 
  and 
  the 
  velocity 
  of 
  the 
  wind 
  over 
  15 
  miles 
  an 
  hour. 
  

   They 
  further 
  show 
  that 
  the 
  young 
  larvae 
  of 
  this 
  insect 
  can 
  be 
  car- 
  

   ried 
  by 
  the 
  wind 
  a 
  third 
  of 
  a 
  mile 
  from 
  a 
  point 
  less 
  than 
  6 
  feet 
  above 
  

   the 
  ground. 
  This 
  being 
  the 
  case, 
  there 
  is 
  an 
  opportunity 
  for 
  exten- 
  

   sive 
  natural 
  spread 
  by 
  the 
  wind. 
  It 
  is 
  not 
  necessary 
  for 
  the 
  velocity 
  

   of 
  the 
  wind 
  to 
  remain 
  constant, 
  as 
  there 
  is 
  doubtless 
  much 
  dispersion 
  

  

  