﻿334 
  REPORT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

  

  THE 
  THORAX. 
  

  

  Notum, 
  

  

  This 
  region 
  of 
  the 
  body 
  is 
  more 
  highly 
  concentrated 
  than 
  in 
  any 
  other 
  

   Phyloptera, 
  not 
  excepting 
  the 
  Trichoptera. 
  The 
  prothorax 
  is 
  a 
  rather 
  

   wide 
  collar, 
  longer 
  and 
  broader 
  than 
  in 
  the 
  Trichoptera, 
  but 
  the 
  meso- 
  

   thorax 
  is 
  spherical 
  and 
  very 
  large 
  in 
  proportion 
  to 
  the 
  metathorax, 
  

   which 
  is 
  rudimentary 
  and 
  but 
  slightly 
  developed 
  ; 
  owing 
  therefore 
  to 
  

   the 
  large 
  mesothorax 
  and 
  the 
  small 
  pro- 
  and 
  metathorax, 
  the 
  entire 
  

   thorax 
  is 
  oval-elliptical, 
  and 
  much 
  consolidated, 
  thus 
  approaching 
  in 
  its 
  

   general 
  appearance 
  the 
  general 
  shape 
  of 
  the 
  Tipulid 
  thorax, 
  or 
  that 
  of 
  

   the 
  lower 
  Lepidoptera. 
  

  

  Pronotum. 
  This 
  forms 
  a 
  broad 
  collar 
  extending 
  backwards 
  on 
  each 
  

   side, 
  the 
  hinder 
  edge 
  being 
  excavated 
  in 
  the 
  middle. 
  

  

  Mesonotum. 
  This 
  is 
  long 
  and 
  well 
  developed, 
  not 
  so 
  wide 
  as 
  the 
  hodj, 
  

   the 
  flanks 
  extending 
  out, 
  when 
  seen 
  from 
  above, 
  beyond 
  the 
  sides 
  of 
  

   the 
  notum. 
  The 
  prsescutum 
  is 
  well 
  developed, 
  forming 
  a 
  round, 
  con- 
  

   vex, 
  swollen 
  sclerite 
  as 
  long 
  as 
  broad, 
  with 
  a 
  median 
  suture-like 
  im- 
  

   pression. 
  The 
  scutum 
  is 
  very 
  large 
  and 
  long, 
  oval, 
  about 
  one- 
  third 
  

   longer 
  than 
  broad, 
  slightly 
  broader 
  behind 
  than 
  in 
  front. 
  

  

  The 
  scutellum 
  is 
  large 
  and 
  well 
  developed, 
  irregularly 
  scutellate 
  in 
  

   outline, 
  with 
  two 
  bosses 
  in 
  front; 
  the 
  posterior 
  end 
  is 
  narrow, 
  truncate 
  

   at 
  the 
  end, 
  with 
  the 
  surface 
  at 
  the 
  end 
  somewhat 
  swollen. 
  

  

  Metanotum. 
  The 
  metathoracic 
  segment 
  is 
  small, 
  very 
  short, 
  and 
  the 
  

   notum 
  and 
  sternum, 
  as 
  also 
  the 
  pleurites, 
  are 
  somewhat 
  rudimentary. 
  

   The 
  surface 
  of 
  the 
  notum 
  is 
  somewhat 
  depressed 
  below 
  the 
  level 
  of 
  the 
  

   mesoscutellum. 
  It 
  is 
  difficult 
  to 
  describe 
  the 
  sclerites. 
  which 
  are 
  rep- 
  

   resented 
  in 
  Fig. 
  1. 
  The 
  entire 
  segment 
  is 
  about 
  one-third 
  as 
  long 
  as 
  

   broad. 
  The 
  scutum 
  is 
  not 
  well 
  differentiated, 
  being 
  represented 
  by 
  a 
  

   median 
  irregular 
  area 
  (Fig. 
  1 
  se'^) 
  about 
  half 
  as 
  long 
  as 
  broad. 
  E'o 
  scu- 
  

   tellum 
  and 
  postscutellum 
  can 
  be 
  distinguished 
  with 
  certainty. 
  

  

  Fletirum, 
  

  

  The 
  sclerites 
  of 
  the 
  flanks 
  are 
  difficult 
  to 
  distinguish. 
  In 
  their 
  de- 
  

   velopment 
  and 
  arrangement 
  the 
  Ephemerina 
  difler 
  from 
  all 
  other 
  Phy- 
  

   Toptera. 
  

  

  Mesopleurum. 
  Though 
  there 
  are 
  a 
  number 
  of 
  sclerites 
  in 
  the 
  meso- 
  

   thorax 
  it 
  is 
  difficult 
  to 
  distinguish 
  what 
  are 
  properly 
  episterna 
  and 
  epi- 
  

   mera. 
  The 
  region 
  of 
  the 
  mesepisternum 
  is 
  indicated 
  in 
  Fig. 
  2 
  epis'', 
  

   and 
  is 
  much 
  larger 
  than 
  the 
  epimeral, 
  which 
  is 
  the 
  region 
  situated 
  over 
  

   the 
  insertion 
  of 
  the 
  middle 
  pair 
  of 
  legs. 
  

  

  The 
  first 
  pair 
  of 
  spiracles 
  is 
  situated 
  on 
  the 
  mesothorax 
  under 
  and 
  

   in 
  front 
  of 
  the 
  insertion 
  of 
  the 
  first 
  pair 
  of 
  wings; 
  the 
  second 
  pair 
  is 
  

   situated 
  on 
  the 
  metathorax 
  directly 
  under 
  the 
  insertion 
  of 
  the 
  second 
  

   pair 
  of 
  wings. 
  

  

  In 
  the 
  metapleurum 
  the 
  episternal 
  region 
  is 
  quite 
  limited 
  and 
  minute 
  

   compared 
  with 
  the 
  large 
  mesepisternal 
  region; 
  what 
  I 
  am 
  inclined 
  to 
  

  

  