﻿44 
  

  

  and 
  destruction 
  of 
  flies 
  by 
  spraying, 
  poisoned 
  bait, 
  traps, 
  etc., 
  

   were 
  carried 
  out. 
  The 
  three 
  favourite 
  breeding-places 
  for 
  flies 
  of 
  

   the 
  house-fly 
  type 
  are 
  horse 
  manure, 
  accumulations 
  of 
  camp 
  and 
  

   cook-house 
  refuse, 
  and 
  latrine 
  trenches, 
  while 
  those 
  of 
  the 
  blue-bottle 
  

   type 
  favour 
  putrefying 
  animal 
  matter. 
  Close 
  packing 
  and 
  spraying 
  

   the 
  manure 
  with 
  sodium 
  arsenite 
  killed 
  the 
  flies 
  in 
  enormous 
  

   quantities 
  Burning 
  was 
  of 
  course 
  quite 
  efficacious 
  where 
  

   practicable. 
  

  

  The 
  numerous 
  items 
  I 
  have 
  just 
  cited 
  will 
  give 
  some 
  idea 
  of 
  the 
  

   multifarious 
  character 
  of 
  the 
  damage 
  caused 
  by 
  insect 
  pests 
  and 
  

   of 
  the 
  ingenuity 
  and 
  study 
  necessary 
  to 
  combat 
  the 
  evil. 
  

  

  Whether 
  it 
  is 
  possible 
  by 
  methods 
  of 
  plant 
  breeding 
  to 
  produce 
  

   varieties 
  having 
  greater 
  freedom 
  from 
  the 
  attacks 
  of 
  insects 
  than 
  

   those 
  now 
  in 
  use, 
  is 
  a 
  field 
  in 
  which 
  much 
  still 
  remains 
  to 
  be 
  

   done. 
  Fernald 
  mentions 
  one 
  case 
  where 
  two 
  New 
  Jersey 
  

   nurseries 
  apparently 
  spread 
  the 
  San 
  Jose 
  Scale 
  over 
  the 
  country 
  in 
  

   their 
  attempts 
  to 
  find 
  a 
  Cnrciilio--pvooi 
  plum; 
  thus 
  one 
  has 
  to 
  be 
  

   careful 
  in 
  attempting 
  to 
  combat 
  one 
  pest, 
  to 
  prevent 
  another 
  

   one 
  taking 
  its 
  place. 
  

  

  Insect 
  outbreaks 
  and 
  their 
  causes 
  are 
  as 
  yet 
  almost 
  entirely 
  

   without 
  explanation, 
  except 
  in 
  such 
  general 
  terms 
  as 
  to 
  leave 
  us 
  

   uncertain 
  when 
  to 
  expect 
  them, 
  and 
  how 
  to 
  prevent 
  or 
  prepare 
  

   to 
  meet 
  them 
  as 
  before. 
  We 
  guess 
  they 
  may 
  be 
  due 
  to 
  

   climatic 
  conditions 
  beyond 
  our 
  control, 
  or 
  perhaps 
  to 
  an 
  unusual 
  

   absence 
  of 
  the 
  natural 
  enemies 
  of 
  the 
  insects 
  concerned, 
  if 
  climatic 
  

   conditions 
  are 
  involved, 
  we 
  lack 
  any 
  knowledge 
  of 
  what 
  these 
  are. 
  

   In 
  1917, 
  the 
  " 
  Whites" 
  especially 
  Pieris 
  bras^icd' 
  were 
  very 
  numerous, 
  

   but 
  the 
  larvae 
  of 
  the 
  latter 
  were 
  so 
  parasitized 
  by 
  the 
  small 
  ichneumon 
  

   fly 
  — 
  Ajtantelea 
  //Imneratns 
  to 
  the 
  extent 
  of 
  90-95%,— 
  that 
  in 
  1918 
  

   brassicce 
  was 
  comparatively 
  scarce. 
  

  

  J. 
  W. 
  McCulloch, 
  in 
  " 
  Journal 
  of 
  Economic 
  Entomology," 
  vol. 
  viii., 
  

   p. 
  245, 
  gives 
  further 
  data 
  on 
  the 
  parasite 
  of 
  the 
  Chinch 
  Bug, 
  

   Kiniiicrosorna 
  henei'ica, 
  Gahan, 
  the 
  egg 
  of 
  the 
  former 
  being 
  largely 
  

   parasitised, 
  ranging 
  from 
  20 
  to 
  40 
  per 
  cent. 
  In 
  the 
  experimental 
  

   work 
  it 
  was 
  shown 
  that 
  the 
  period 
  of 
  oviposition 
  of 
  the 
  Chinch 
  Bug 
  

   covered 
  about 
  2 
  months, 
  while 
  the 
  life-cycle 
  of 
  the 
  parasite 
  extended 
  

   over 
  a 
  period 
  of 
  only 
  2 
  or 
  3 
  weeks. 
  Thus 
  the 
  eggs 
  of 
  a 
  single 
  

   female 
  Chinch 
  Bug 
  were 
  exposed 
  to 
  about 
  3 
  broods 
  of 
  parasites, 
  

   while 
  the 
  eggs 
  of 
  one 
  brood 
  of 
  Chinch 
  Bug 
  were 
  exposed 
  to 
  4 
  or 
  5 
  

   broods 
  of 
  parasites. 
  

  

  Erom 
  this 
  data 
  it 
  is 
  conservative 
  to 
  estimate 
  the 
  parasitism 
  in 
  the 
  

  

  