﻿AIR-SACS 
  OF 
  THE 
  LOCUST. 
  179 
  

  

  in 
  purely 
  creeping 
  and 
  running 
  insects, 
  but 
  only 
  in 
  those 
  which 
  leap 
  

   and 
  always 
  in 
  those 
  which 
  fly. 
  In 
  the 
  two-winged 
  flies 
  (Biptera) 
  the 
  

   vesicles 
  are 
  both 
  large 
  and 
  numerous, 
  as 
  any 
  one 
  can 
  see 
  by 
  opening 
  the 
  

   body 
  of 
  the 
  common 
  house 
  fly. 
  

  

  According 
  to 
  Marcel 
  d^ 
  Series, 
  the 
  Asilidce 
  have 
  an 
  immense 
  number 
  of 
  small 
  

   elongated 
  vesicles 
  on 
  eacli 
  side. 
  In 
  one 
  species 
  they 
  amount 
  to 
  so 
  many 
  as 
  sixty. 
  

   Burmeister 
  remarks 
  that 
  in 
  the 
  Lepiloptera 
  vesicles 
  in 
  the 
  Sphingidce 
  and 
  moths 
  are 
  

   chiefly 
  found 
  in 
  the 
  males, 
  which 
  agrees 
  with 
  our 
  own 
  observations 
  in 
  Hymenoptera. 
  

  

  The 
  air-sacs 
  in 
  the 
  family 
  of 
  locusts 
  (Acrydii) 
  are 
  as 
  numerous 
  and 
  there 
  

   are 
  as 
  many 
  large 
  ones 
  as 
  in 
  any 
  group 
  of 
  insects, 
  the 
  females 
  being 
  as 
  

   well 
  provided 
  with, 
  them 
  as 
  the 
  males. 
  'jlo 
  the 
  general 
  accouut 
  given 
  

   in 
  our 
  First 
  Keport 
  (pp. 
  267-270) 
  we 
  may 
  add 
  a 
  few 
  facts, 
  and 
  present 
  

   in 
  Plate 
  I 
  some 
  enlarged 
  views 
  of 
  ti:e 
  upper 
  side 
  of 
  the 
  head 
  and 
  the 
  face, 
  

   showing 
  better 
  than 
  in 
  the 
  wood-cuts 
  in 
  the 
  First 
  Report 
  their 
  mode 
  of 
  

   distribution. 
  Without 
  repeating 
  the 
  distribution 
  of 
  the 
  air-sacs 
  in 
  the 
  

   head 
  the 
  reader 
  is 
  referred 
  to 
  page 
  269 
  of 
  the 
  First 
  Report 
  and 
  to 
  Figs. 
  

   1 
  and 
  2 
  of 
  Plate 
  I 
  of 
  the 
  present 
  report. 
  

  

  Our 
  Fig. 
  3 
  (Plate 
  I) 
  represents 
  the 
  course 
  of 
  the 
  main 
  ventral 
  tra- 
  

   cheae 
  or 
  air-tubes 
  extending 
  along 
  the 
  floor 
  of 
  the 
  hind-body 
  or 
  abdomen 
  

   under 
  the 
  digestive 
  canal. 
  They 
  are 
  indicated 
  in 
  Fig. 
  16 
  V 
  of 
  the 
  First 
  

   Report. 
  In 
  that 
  figure, 
  however, 
  the 
  relation 
  of 
  this 
  ventral 
  system 
  of 
  

   air 
  tubes 
  to 
  the 
  air-sacs 
  is 
  not 
  shown. 
  By 
  reference 
  to 
  our 
  figure 
  on 
  

   Plate 
  I 
  it 
  will 
  be 
  seen 
  that 
  from 
  these 
  tubes 
  arise 
  small 
  tracheal 
  twigs 
  

   in 
  the 
  thorax, 
  which 
  give 
  off 
  numerous 
  minute 
  globular 
  or 
  oval 
  air-sacs; 
  

   these 
  are 
  also 
  very 
  abundant 
  at 
  the 
  base 
  of 
  the 
  abdomen, 
  especially 
  in 
  

   the 
  front 
  and 
  hinder 
  part 
  of 
  the 
  first 
  or 
  basal 
  segment 
  of 
  the 
  abdomen, 
  

   while 
  a 
  few 
  line 
  the 
  walls 
  behind, 
  and 
  others 
  are 
  seen 
  near 
  the 
  middle 
  

   of 
  the 
  abdomen 
  in 
  the 
  fourth 
  segment. 
  Again 
  they 
  become 
  noticeable 
  

   in 
  the 
  end 
  of 
  the 
  abdomen 
  near 
  the 
  base 
  of 
  the 
  ovipositor, 
  where 
  the 
  

   smaller 
  twigs 
  from 
  the 
  ends 
  of 
  the 
  two 
  main 
  tracheae 
  each 
  end 
  in 
  numer- 
  

   ous 
  small 
  sacs. 
  

  

  Fig. 
  4 
  of 
  the 
  same 
  plate 
  represents 
  the 
  distribution 
  of 
  the 
  air-tubes 
  in 
  

   the 
  hind 
  legs 
  of 
  a 
  common 
  locust 
  ((Edipoda 
  sordida). 
  In 
  the 
  fore 
  and 
  

   middle 
  as 
  well 
  as 
  hinder 
  pair 
  of 
  legs, 
  the 
  thigh 
  joint 
  (femur) 
  is 
  provided 
  

   with 
  two 
  large 
  dilated 
  air-tubes, 
  but 
  there 
  are 
  only 
  four 
  minute, 
  slender 
  

   air-sacs 
  at 
  the 
  base 
  (not 
  represented 
  in 
  the 
  drawing). 
  At 
  the 
  end 
  of 
  

   the 
  femur 
  these 
  two 
  tubes 
  dilate 
  or 
  expand 
  considerably. 
  A 
  large 
  di- 
  

   lated 
  air- 
  tube 
  (t. 
  tr), 
  with 
  numerous 
  small 
  branches, 
  passes 
  along 
  through 
  

   the 
  shin-joint 
  or 
  tibia, 
  lying 
  between 
  the 
  muscles, 
  and 
  this 
  trachea 
  ex- 
  

   tends 
  through 
  the 
  five 
  toe-joints, 
  ending 
  in 
  several 
  small 
  branches 
  in 
  the 
  

   fifth 
  joint 
  at 
  the 
  insertion 
  of 
  the 
  claws. 
  

  

  Use 
  of 
  the 
  air-sacs 
  in 
  flight. 
  — 
  We 
  described 
  in 
  our 
  First 
  Report 
  (pp. 
  

   269, 
  270) 
  the 
  mode 
  of 
  inhalation 
  of 
  the 
  air, 
  or 
  of 
  breathing 
  in 
  the 
  locust, 
  

   and 
  briefly 
  pointed 
  out 
  the 
  way 
  in 
  which 
  the 
  air-sacs 
  are 
  filled 
  by 
  the 
  

   air 
  drawn 
  in 
  through 
  the 
  spiracle 
  or 
  breathing 
  holes. 
  It 
  thus 
  appears 
  

  

  