﻿180 
  REPORT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

  

  that 
  the 
  powers 
  of 
  the 
  locust 
  as 
  an 
  aeronaut 
  are 
  as 
  great 
  or 
  greater 
  than 
  

   in 
  any 
  other 
  kind 
  of 
  insect. 
  

  

  That 
  the 
  use 
  of 
  the 
  air-sacs 
  is 
  to 
  buoy 
  up 
  the 
  insect 
  in 
  the 
  air, 
  and 
  

   that 
  by 
  filling 
  and 
  partially 
  emptying 
  the 
  sacs 
  during 
  the 
  process 
  of 
  

   breathing 
  the 
  insect 
  can 
  enlarge 
  its 
  bulk 
  and 
  change 
  its 
  specific 
  grav- 
  

   ity 
  at 
  will, 
  so 
  as 
  to 
  render 
  itself 
  capable 
  of 
  supporting 
  itself 
  on 
  the 
  wing 
  

   with 
  little 
  effort, 
  was 
  first 
  discovered 
  by 
  Sir 
  John 
  Hunter. 
  Newport, 
  in 
  

   his 
  treatise 
  on 
  insects, 
  remarks 
  : 
  

  

  That 
  this 
  is 
  the 
  use 
  of 
  the 
  sacs 
  may 
  be 
  inferred 
  from 
  their 
  non-existeDce 
  in 
  the 
  

   larva 
  state, 
  or 
  in 
  insects 
  that 
  constantly 
  reside 
  on 
  the 
  ground, 
  more 
  particularly 
  in 
  

   creeping 
  insects 
  ; 
  and 
  it 
  seems 
  further 
  confirmed 
  by 
  the 
  fact 
  that 
  among 
  volant 
  in- 
  

   sects 
  those 
  have 
  the 
  largest 
  and 
  greatest 
  number 
  of 
  vesicles 
  which 
  sustain 
  the 
  

   longest 
  and 
  most 
  powerful 
  flight. 
  Thus 
  the 
  vesicles 
  are 
  found 
  most 
  developed 
  in 
  

   the 
  Hymenoptera, 
  Lepidoptera 
  Diptera, 
  and 
  some 
  Coleoptera, 
  and 
  Hemiptera, 
  in 
  all 
  

   which, 
  in 
  the 
  larva 
  state, 
  there 
  is 
  not 
  the 
  slightest 
  trace 
  of 
  them. 
  A 
  still 
  further 
  

   proof 
  that 
  they 
  are 
  for 
  lightening 
  the 
  body 
  is 
  found 
  in 
  Lucanus 
  cervus. 
  In 
  the 
  male 
  

   of 
  this 
  insect 
  the 
  large 
  and 
  heavy 
  mandibles 
  and 
  head, 
  but 
  more 
  especially 
  the 
  man- 
  

   dibles, 
  are 
  not 
  filled 
  with 
  solid 
  muscle, 
  as 
  in 
  the 
  Hydrous 
  and 
  others 
  in 
  which 
  these 
  

   parts 
  are 
  more 
  in 
  proportion 
  to 
  the 
  size 
  of 
  other 
  parts 
  of 
  the 
  body, 
  but 
  with 
  an 
  im- 
  

   mense 
  number 
  of 
  vesicles, 
  which 
  in 
  the 
  mandibles 
  are 
  developed 
  in 
  the 
  greatest 
  

   abundance 
  in 
  sacs 
  from 
  long 
  tracheae, 
  that 
  are 
  extended 
  from 
  one 
  end 
  of 
  the 
  organ 
  

   to 
  the 
  other, 
  so 
  that 
  the 
  interior 
  is 
  almost 
  entirely 
  filled 
  with 
  vesicles. 
  By 
  this 
  beau- 
  

   tiful 
  provision 
  these 
  projecting 
  and 
  apparently 
  unwieldy 
  structures 
  are 
  rendered 
  ex- 
  

   ceedingly 
  light, 
  while 
  their 
  solid 
  interior 
  fits 
  them 
  for 
  all 
  the 
  purposes 
  of 
  strength 
  

   required 
  by 
  the 
  insect. 
  The 
  large 
  and 
  apparently 
  heavy 
  body 
  of 
  the 
  humble-bee 
  is 
  

   lightened 
  in 
  a 
  similar 
  manner. 
  In 
  this 
  insect 
  and 
  others 
  of 
  the 
  same 
  order 
  the 
  vesi- 
  

   cles 
  are 
  fewer, 
  but 
  very 
  much 
  larger 
  than 
  in 
  Coleoptera. 
  The 
  lateral 
  tracheae 
  in 
  the 
  

   abdomen 
  form 
  one 
  continuous 
  chain 
  of 
  dilatations, 
  which 
  are 
  larger 
  in 
  the 
  males 
  of 
  

   the 
  species 
  than 
  in 
  the 
  females. 
  220 
  

  

  Also, 
  in 
  his 
  article 
  " 
  on 
  the 
  formation 
  and 
  use 
  of 
  the 
  air-sacs 
  and 
  di- 
  

   lated 
  trachead 
  in 
  insects," 
  221 
  Newport 
  gives 
  further 
  information 
  regard- 
  

   ing 
  the 
  presence 
  of 
  these 
  sacs 
  in 
  other 
  insects 
  : 
  

  

  In 
  the 
  most 
  active 
  Neuroptera 
  the 
  sacs 
  are 
  very 
  numerous 
  and 
  capacious, 
  especially 
  

   in 
  the 
  dragon-flies, 
  but 
  they 
  are 
  much 
  smaller 
  and 
  fewer 
  in 
  number 
  in 
  the 
  Ephemeras, 
  

   the 
  Sialidw, 
  and 
  the 
  scorpion-flies. 
  In 
  the 
  Coleoptera 
  the 
  sacs 
  exist 
  only 
  in 
  the 
  volant 
  

   species, 
  and 
  are 
  more 
  or 
  less 
  numerous 
  and 
  capacious 
  in 
  these 
  in 
  proportion 
  to 
  the 
  

   bulkiness 
  of 
  the 
  insect 
  and 
  its 
  degree 
  of 
  activity 
  on 
  the 
  wing. 
  This 
  difference 
  exists 
  

   not 
  only 
  in 
  different 
  genera, 
  but 
  in 
  different 
  species 
  of 
  the 
  same 
  genus, 
  according 
  as 
  

   they 
  are 
  winged 
  or 
  apterous 
  species. 
  Thus 
  distinct 
  vesicles 
  are 
  found 
  in 
  the 
  winged 
  

   Carabidce, 
  but 
  not 
  in 
  the 
  apterous, 
  in 
  which 
  the 
  respiratory 
  organs 
  are 
  simply 
  tracheal. 
  

   In 
  the 
  more 
  heavy-bodied 
  genera 
  the 
  vesicles 
  are 
  not 
  confined 
  to 
  the 
  abdominal 
  and 
  

   thoracic 
  regions, 
  but 
  are 
  sometimes 
  extended 
  into 
  other 
  parts, 
  as 
  in 
  the 
  unwieldy 
  

   stag-beetles, 
  in 
  which 
  they 
  are 
  extremely 
  numerous, 
  and 
  occupy 
  the 
  chief 
  portion 
  of 
  

   the 
  interior 
  of 
  the 
  mandibles. 
  In 
  the 
  Lepidoptera, 
  as 
  in 
  the 
  Neuroptera, 
  they 
  are 
  

   largest 
  in 
  the 
  swiftest 
  and 
  most 
  powerful 
  species, 
  and 
  more 
  especially 
  so 
  in 
  those 
  in 
  

   the 
  males, 
  which 
  are 
  known 
  to 
  be 
  most 
  active 
  on 
  the 
  wing. 
  On 
  the 
  contrary, 
  in 
  tho 
  

   majority 
  of 
  the 
  Orthoptera, 
  which 
  are 
  merely 
  saltatorial 
  in 
  their 
  habits, 
  the 
  trachese 
  

   never 
  assume 
  the 
  form 
  of 
  distinct 
  vesicles, 
  excepting 
  in 
  a 
  few 
  genera, 
  which 
  have 
  the 
  

   power 
  of 
  flight. 
  They 
  retain 
  tho 
  arborescent 
  form 
  in 
  the 
  perfect 
  as 
  in 
  the 
  larva 
  state, 
  

   but 
  are 
  considerably 
  enlarged 
  throughout 
  the 
  greater 
  part 
  of 
  their 
  course, 
  their 
  ex- 
  

  

  220 
  Todd's 
  Cyclopaedia 
  of 
  Anatomy 
  and 
  Physiology. 
  Article, 
  Insecta. 
  

  

  wi 
  Transactions 
  of 
  the 
  Linnaean 
  Society 
  of 
  London, 
  1851, 
  vol. 
  xx, 
  p. 
  419^23. 
  

  

  