﻿98 
  Mr. 
  J. 
  W. 
  Douglas 
  on 
  the 
  

  

  parts 
  of 
  plants, 
  the 
  smallest 
  are 
  those 
  which 
  find 
  sufficient 
  accom- 
  

   modation 
  in 
  the 
  interior 
  of 
  leaves, 
  and 
  even 
  in 
  the 
  thinnest. 
  These 
  

   insects 
  insinuate 
  themselves 
  and 
  form 
  paths 
  between 
  the 
  upper 
  

   and 
  under 
  skins 
  of 
  the 
  leaves, 
  where 
  they 
  are 
  well 
  sheltered 
  ; 
  they 
  

   mine 
  in 
  the 
  fleshy 
  substance 
  of 
  the 
  leaf 
  and 
  loosen 
  the 
  paren- 
  

   chyma 
  ; 
  no 
  rubbish 
  from 
  the 
  space 
  that 
  they 
  enlarge 
  inconve- 
  

   niences 
  them 
  ; 
  they 
  eat 
  all 
  that 
  they 
  loosen, 
  and 
  so 
  their 
  labour 
  

   answers 
  two 
  purposes 
  ; 
  for 
  at 
  the 
  same 
  time 
  that 
  they 
  are 
  en- 
  

   larging 
  their 
  habitation 
  they 
  are 
  procuring 
  their 
  food. 
  

  

  " 
  The 
  insects 
  which 
  mine 
  in 
  leaves, 
  though 
  small, 
  are 
  easily 
  

   found. 
  One 
  needs 
  only 
  to 
  see 
  the 
  outside 
  of 
  a 
  leaf, 
  to 
  know 
  

   whether 
  there 
  is 
  a 
  mining 
  larva 
  within 
  ; 
  though 
  green 
  and 
  healthy 
  

   every 
  where 
  else, 
  it 
  is 
  dried 
  up, 
  yellowish, 
  whitish, 
  or 
  at 
  least 
  of 
  a 
  

   different 
  hue 
  from 
  the 
  rest, 
  at 
  the 
  places 
  which 
  the 
  insect 
  occu- 
  

   pies, 
  or 
  has 
  inhabited. 
  The 
  form 
  of 
  these 
  mined 
  places 
  shows 
  us 
  

   that 
  these 
  insects 
  have 
  three 
  different 
  ways 
  of 
  conducting 
  their 
  

   labours 
  in 
  the 
  interior 
  of 
  leaves. 
  Some 
  form 
  only 
  narrow, 
  long, 
  

   and 
  tortuous 
  galleries, 
  the 
  forms 
  of 
  which 
  are 
  extremely 
  irre- 
  

   gular 
  ; 
  others, 
  wishing 
  to 
  have 
  more 
  room, 
  mine 
  irregular, 
  ob- 
  

   long, 
  larger 
  places 
  ; 
  and 
  others, 
  which 
  when 
  young 
  have 
  mined 
  

   in 
  galleries, 
  when 
  full 
  grown 
  mine 
  in 
  large 
  patches." 
  

  

  Note. 
  — 
  Those 
  larvae 
  living 
  in 
  galleries 
  are 
  all, 
  as 
  far 
  as 
  we 
  are 
  

   at 
  present 
  informed, 
  of 
  the 
  genus 
  Neplicula 
  ; 
  possibly 
  Tr'ifurcula 
  

   also 
  mines 
  in 
  galleries, 
  but 
  that 
  is 
  not 
  yet 
  ascertained, 
  no 
  species 
  of 
  

   the 
  latter 
  genus 
  having 
  been 
  bred. 
  The 
  gallery 
  of 
  a 
  Nepticida 
  may, 
  

   I 
  believe, 
  be 
  always 
  distinguished 
  from 
  that 
  of 
  a 
  Dipterous 
  larva 
  

   by 
  the 
  excrement 
  forming 
  an 
  uninterrupted 
  line 
  ; 
  in 
  the 
  galleries 
  

   mined 
  by 
  Dipterous 
  larva?, 
  the 
  excrement 
  is 
  scattered 
  here 
  and 
  

   there, 
  as 
  may 
  be 
  easily 
  seen 
  in 
  the 
  leaves 
  of 
  buttercup, 
  holly, 
  

   honeysuckle, 
  meadowsweet, 
  &c. 
  &c. 
  

  

  " 
  Although 
  the 
  class 
  of 
  insects 
  which 
  mine 
  in 
  leaves 
  has 
  as 
  yet 
  

   (1737) 
  been 
  little 
  observed, 
  it 
  already 
  includes 
  a 
  great 
  number 
  of 
  

   species. 
  There 
  are 
  few 
  trees 
  or 
  plants, 
  if 
  there 
  are 
  any, 
  that 
  are 
  

   not 
  attacked 
  by 
  some 
  mining 
  larva. 
  There 
  are 
  even 
  miners 
  of 
  

   different 
  species 
  in 
  the 
  leaves 
  of 
  the 
  same 
  plant 
  or 
  tree 
  ; 
  and 
  we 
  

   see 
  not 
  only 
  the 
  different 
  leaves 
  of 
  an 
  apple 
  tree, 
  but 
  even 
  one 
  

   leaf 
  of 
  the 
  same 
  tree, 
  mined 
  both 
  in 
  galleries 
  and 
  blotches. 
  Pro- 
  

   bably 
  the 
  same 
  tree 
  furnishes 
  food 
  to 
  gallery-miners 
  and 
  blotch- 
  

   miners 
  of 
  several 
  species." 
  

  

  Note. 
  — 
  I 
  have 
  in 
  one 
  apple 
  leaf 
  observed 
  several 
  larvae 
  of 
  each 
  

   of 
  the 
  three 
  species, 
  Lithocolletis 
  PomifolieUa, 
  Cemiostoma 
  scitella 
  

   and 
  NejJticula 
  ? 
  

  

  " 
  It 
  is 
  sometimes 
  difficult 
  to 
  perceive 
  in 
  what 
  these 
  species 
  of 
  

   such 
  small 
  insects 
  differ 
  from 
  each 
  other 
  ; 
  besides, 
  it 
  is 
  not 
  cer- 
  

  

  