﻿82 
  DECIDUOUS 
  FRUIT 
  INSECTS 
  AND 
  INSECTICIDES. 
  

  

  was 
  rather 
  resistant 
  against 
  the 
  burning 
  effect 
  of 
  the 
  spray 
  materials. 
  

   Twigs 
  bearing 
  from 
  20 
  to 
  30 
  leaves 
  were 
  employed. 
  

  

  The 
  spray 
  was 
  applied 
  to 
  the 
  foliage 
  by 
  means 
  of 
  a 
  large 
  atomizer 
  

   of 
  the 
  type 
  hi 
  which 
  quart 
  jars 
  are 
  used 
  as 
  a 
  container 
  for 
  the 
  liquid. 
  

   The 
  twigs 
  were 
  sprayed 
  until 
  the 
  leaves 
  began 
  to 
  drip, 
  approaching 
  

   as 
  nearly 
  as 
  possible 
  the 
  conditions 
  of 
  field 
  spraying 
  operations. 
  

   Each 
  sprayed 
  twig 
  was 
  then 
  placed 
  in 
  a 
  jelly 
  glass 
  of 
  water, 
  the 
  

   stem 
  extending 
  through 
  a 
  hole 
  punched 
  in 
  the 
  tin 
  cover. 
  (See 
  Plate 
  

   XI, 
  figs. 
  1, 
  2.) 
  

  

  After 
  the 
  spray 
  had 
  thoroughly 
  dried, 
  allowing 
  from 
  6 
  to 
  12 
  hours, 
  

   20 
  insects 
  were 
  placed 
  on 
  the 
  leaves 
  of 
  each 
  twig. 
  A 
  large 
  paper 
  

   bag 
  was 
  then 
  placed 
  over 
  the 
  twig 
  and 
  held 
  to 
  the 
  glass 
  by 
  means 
  of 
  a 
  

   rubber 
  band. 
  (See 
  Plate 
  XI, 
  Hg. 
  1, 
  at 
  right.) 
  

  

  Observations 
  were 
  usually 
  made 
  every 
  other 
  day; 
  in 
  some 
  cases 
  

   every 
  day. 
  At 
  each 
  examination 
  the 
  bag 
  was 
  removed 
  and 
  the 
  dead 
  

   larvae 
  taken 
  out 
  and 
  counted. 
  When 
  all 
  the 
  insects 
  were 
  dead, 
  or 
  

   had 
  pupated, 
  as 
  the 
  case 
  might 
  be, 
  the 
  amount 
  of 
  foliage 
  consumed 
  

   was 
  measured 
  in 
  square 
  inches. 
  A 
  sheet 
  of 
  celluloid 
  cross-sectioned 
  

   to 
  one 
  one-hundredth 
  of 
  a 
  square 
  inch 
  was 
  utilized 
  for 
  this 
  purpose. 
  

   These 
  measurements 
  were 
  easily 
  taken, 
  where 
  effective 
  poisons 
  

   were 
  used, 
  as 
  the 
  young 
  larvae 
  died 
  before 
  very 
  much 
  foliage 
  had 
  

   been 
  consumed. 
  The 
  younger 
  larvae 
  ate 
  only 
  one 
  surface 
  of 
  the 
  leaf, 
  

   but 
  as 
  they 
  increased 
  in 
  size 
  the 
  leaves 
  were 
  often 
  skeletonized. 
  

   Owing 
  to 
  this 
  fact 
  it 
  became 
  necessary 
  to 
  differentiate 
  between 
  the 
  

   one 
  and 
  two 
  surface 
  feedings. 
  Therefore, 
  in 
  order 
  to 
  equalize 
  these 
  

   conditions, 
  the 
  measurements 
  of 
  the 
  one 
  surface 
  feeding 
  were 
  divided 
  

   by 
  two. 
  Another 
  difficulty 
  in 
  securing 
  feeding 
  measurements 
  in 
  the 
  

   case 
  of 
  unsprayed 
  twigs 
  used 
  as 
  checks 
  was 
  encountered 
  when 
  the 
  

   entire 
  leaf, 
  except 
  the 
  midrib 
  and 
  larger 
  veins, 
  was 
  consumed. 
  In 
  

   such 
  instances 
  the 
  outline 
  of 
  the 
  leaf 
  was 
  nearly 
  obliterated, 
  thus 
  

   rendering 
  actual 
  measurements 
  in 
  the 
  ordinary 
  way 
  impossible. 
  

   However, 
  since 
  the 
  leaves 
  of 
  the 
  wild 
  cherry 
  selected 
  for 
  the 
  experi- 
  

   ments 
  were 
  fairly 
  uniform 
  in 
  size, 
  this 
  difficulty 
  was 
  overcome 
  by 
  

   taking 
  the 
  measurement 
  of 
  an 
  average-size 
  leaf 
  and 
  substituting 
  it 
  

   for 
  the 
  leaf 
  the 
  outline 
  of 
  which 
  had 
  been 
  destroyed. 
  This 
  method 
  

   gave 
  approximately 
  accurate 
  results. 
  Careful 
  attention 
  was 
  given 
  

   to 
  the 
  condition 
  of 
  the 
  foliage 
  throughout 
  the 
  experiments 
  so 
  as 
  to 
  

   supply 
  the 
  larvae 
  with 
  palatable 
  food 
  at 
  all 
  times. 
  It 
  was 
  seldom 
  

   necessary, 
  however, 
  to 
  renew 
  the 
  foliage, 
  except 
  for 
  the 
  unsprayed 
  

   lots, 
  which 
  were 
  quickly 
  devoured. 
  

  

  Commercial 
  lime-sulphur 
  testing 
  33° 
  Baume 
  was 
  used 
  at 
  strengths 
  

   varying 
  from 
  |-50 
  to 
  6-50. 
  x 
  In 
  lots 
  4 
  and 
  5 
  of 
  Table 
  VI 
  home- 
  

   boiled 
  lime-sulphur 
  testing 
  30° 
  Baume 
  was 
  used 
  at 
  the 
  rate 
  of 
  1^-50. 
  

  

  i 
  All 
  the 
  strengths 
  indicated 
  as 
  above 
  signify 
  a 
  given 
  quantity 
  of 
  poison 
  diluted 
  with 
  water 
  to 
  make 
  a 
  

   total 
  of 
  50 
  gallons 
  of 
  spray 
  material. 
  For 
  example, 
  lime-sulphur, 
  l£-50, 
  means 
  1£ 
  gallons 
  concentrated 
  

   lime-sulphur 
  solution 
  diluted 
  with 
  water 
  to 
  make 
  50 
  gallons 
  of 
  spray 
  material. 
  Arsenate 
  of 
  lead, 
  2-50, 
  

   means 
  2 
  pounds 
  arsenate 
  of 
  lead 
  diluted 
  with 
  water 
  to 
  make 
  50 
  gallons 
  of 
  spray 
  material. 
  

  

  