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  alone, 
  nor 
  with 
  farming 
  alone. 
  One 
  may 
  be 
  a 
  most 
  excellent 
  

   entomologist, 
  or 
  botanist, 
  or 
  he 
  may 
  have 
  the 
  whole 
  theory 
  and 
  

   practice 
  of 
  agriculture 
  at 
  his 
  tongue's 
  end, 
  and 
  yet 
  be 
  without 
  

   knowledge 
  or 
  resource, 
  when 
  brought 
  face 
  to 
  face 
  with 
  a 
  new 
  

   practical 
  problem 
  in 
  economic 
  entomology. 
  The 
  subject 
  is 
  

   essentially 
  that 
  of 
  the 
  relations 
  of 
  these 
  things 
  to 
  each 
  other, 
  of 
  

   insect 
  to 
  plant, 
  and 
  plant 
  to 
  insect, 
  and 
  of 
  both 
  these 
  to 
  the 
  

   purposes 
  and 
  operations 
  of 
  the 
  farm, 
  and 
  it 
  involves 
  some 
  know- 
  

   ledge 
  of 
  all 
  of 
  them. 
  

  

  "The 
  life-histories 
  of 
  insects 
  lie 
  at 
  the 
  foundation 
  of 
  the 
  whole 
  

   subject 
  of 
  economic 
  entomology, 
  and 
  constitute 
  in 
  fact 
  the 
  

   principal 
  part 
  of 
  the 
  science, 
  for 
  until 
  these 
  are 
  clearly 
  and 
  

   completely 
  made 
  out 
  for 
  any 
  given 
  injurious 
  species, 
  we 
  cannot 
  

   possibly 
  tell 
  when, 
  where, 
  or 
  how 
  to 
  strike 
  it 
  at 
  its 
  weakest 
  point. 
  

   Besides 
  this, 
  we 
  must 
  also 
  know 
  the 
  conditions 
  favourable 
  and 
  

   unfavourable 
  to 
  it, 
  the 
  enemies 
  which 
  prey 
  upon 
  it, 
  whether, 
  bird 
  

   or 
  insect, 
  or 
  plant 
  parasite, 
  the 
  diseases 
  to 
  which 
  it 
  is 
  subject, 
  

   and 
  the 
  effects 
  of 
  the 
  various 
  changes 
  of 
  weather 
  and 
  season 
  ; 
  we 
  

   should 
  make 
  in 
  fact 
  a 
  thorough 
  study 
  of 
  it 
  in 
  relation 
  to 
  the 
  

   whole 
  system 
  of 
  things 
  by 
  which 
  it 
  is 
  affected. 
  

  

  " 
  Without 
  this 
  we 
  shall 
  often 
  be 
  exposed 
  to 
  needless 
  alarm 
  

   and 
  expense, 
  perhaps 
  in 
  fighting 
  by 
  artificial 
  remedies 
  an 
  insect 
  

   already 
  in 
  process 
  of 
  rapid 
  extinction 
  by 
  natural 
  causes, 
  Ave 
  may 
  

   even 
  for 
  lack 
  of 
  this 
  knowledge 
  destroy 
  our 
  best 
  friends 
  under 
  

   the 
  supposition 
  that 
  they 
  are 
  the 
  authors 
  of 
  the 
  mischief 
  which 
  

   they 
  are 
  really 
  exerting 
  themselves 
  to 
  prevent, 
  and 
  we 
  must 
  also 
  

   learn 
  where 
  strictly 
  artificial 
  measures 
  can 
  be 
  used 
  to 
  advantage 
  

   to 
  destroy 
  or 
  prevent 
  them 
  ; 
  it 
  is 
  obvious 
  that 
  of 
  the 
  life- 
  

   histories 
  of 
  insects, 
  close, 
  accurate 
  and 
  continuous 
  observation 
  is 
  

   necessary." 
  

  

  Injurious 
  insects 
  occur 
  among 
  the 
  following 
  orders, 
  Coleoptera, 
  

   Hymenoptera, 
  Lepidoptera, 
  Diptera, 
  Hemiptera 
  (both 
  Heteroptera 
  

   and 
  Homoptera), 
  Orthoptera, 
  Neuroptera, 
  Thysanoptera 
  and 
  Aptera. 
  

  

  But 
  whilst 
  there 
  are 
  many 
  injurious 
  insects, 
  there 
  are 
  also 
  many 
  

   beneficial 
  ones, 
  and 
  Folsom 
  quotes 
  a 
  case 
  m 
  which 
  the 
  fluted-scale 
  

   has 
  been 
  nearly 
  exterminated 
  in 
  California, 
  by 
  the 
  lady-bird 
  beetle, 
  

   Novitis 
  cardinalis 
  ; 
  and 
  how 
  over 
  3000 
  specimens 
  of 
  a 
  Hymenopterous 
  

   parasite, 
  Cnpidosmna 
  truncatellmn, 
  were 
  reared 
  by 
  Giard 
  from 
  a 
  single 
  

   Pliinia 
  larva. 
  

  

  Beneficial 
  insects 
  must 
  be 
  also 
  considered. 
  The 
  most 
  important 
  

   friends 
  of 
  the 
  farmer 
  and 
  gardener 
  are 
  the 
  Hymenopterous 
  families 
  

  

  