﻿ODONATA. 
  331 
  

  

  ble 
  from 
  above. 
  Scutum 
  sub 
  trapezoidal, 
  longer 
  than 
  broad 
  5 
  acute 
  

   behind, 
  with 
  an 
  appendicular 
  area 
  between 
  the 
  conical 
  end 
  and 
  the 
  scu- 
  

   tellum, 
  consisting 
  of 
  two 
  diverging 
  tubercles, 
  from 
  which 
  a 
  narrow 
  ridge 
  

   falls 
  away 
  on 
  each 
  side, 
  forming 
  the 
  origin 
  of 
  the 
  5th 
  vein 
  of 
  the 
  wings 
  

   on 
  each 
  side. 
  (Fig. 
  3, 
  v. 
  5.) 
  

  

  The 
  scutellum 
  is 
  swollen, 
  triangular, 
  as 
  broad 
  as 
  long, 
  the 
  apex 
  

   directed 
  backwards 
  and 
  wedged 
  in 
  between 
  the 
  separate 
  halves 
  of 
  the 
  

   post-scutellum, 
  which 
  is 
  represented 
  by 
  two 
  triangular 
  bosses, 
  the 
  apices 
  

   separated 
  by 
  the 
  pointed 
  end 
  of 
  the 
  scutellum, 
  the 
  bases 
  connected 
  by 
  a 
  

   ridge 
  concealed 
  by 
  the 
  end 
  of 
  the 
  scutellum. 
  

  

  Metanotum, 
  (Fig. 
  4.) 
  There 
  is 
  a 
  pair 
  of 
  patagia, 
  one 
  in 
  front 
  of 
  the 
  

   base 
  of 
  each 
  hind 
  wing. 
  No 
  praescutum. 
  The 
  scutum 
  is 
  much 
  larger 
  

   than 
  the 
  mesoscutum, 
  a 
  little 
  longer 
  than 
  broad; 
  each 
  side 
  raised 
  into 
  

   an 
  oblong-oval 
  boss, 
  with 
  a 
  narrow, 
  acute, 
  triangular, 
  depressed, 
  flat 
  

   area 
  between, 
  and 
  bounded 
  behind 
  by 
  a 
  converging 
  ridge, 
  which 
  is 
  suc- 
  

   ceeded 
  by 
  a 
  peculiar 
  diverging 
  ridge 
  (v. 
  5), 
  like 
  that 
  in 
  the 
  mesonotum, 
  

   which 
  is 
  the 
  origin 
  of 
  the 
  5th 
  vein 
  of 
  the 
  second 
  pair 
  of 
  wings. 
  

  

  The 
  scutellum 
  is 
  much 
  larger 
  than 
  in 
  the 
  mesonotum, 
  nearly 
  square, 
  

   smooth 
  and 
  flat 
  ; 
  the 
  posterior 
  one-half 
  vertical, 
  thin, 
  and 
  more 
  or 
  less 
  

   elastic 
  and 
  membranous, 
  moving 
  upon 
  the 
  abdomen. 
  (This 
  posterior 
  

   portion 
  may 
  represent 
  the 
  post-scutellum, 
  which 
  is 
  otherwise 
  absent, 
  but 
  

   there 
  are 
  no 
  signs 
  of 
  a 
  suture.) 
  Post-scutellum 
  absent 
  (?) 
  See 
  Fig. 
  4, 
  

   p. 
  scl/^, 
  for 
  what 
  may 
  prove 
  to 
  be 
  the 
  post-scutellum. 
  

  

  Pleurum, 
  

  

  In 
  Agrion 
  (Fig. 
  7) 
  the 
  pro-episternum 
  and 
  epimerum 
  of 
  each 
  side 
  are 
  

   minute, 
  rudimentary, 
  and 
  sub 
  membranous, 
  and 
  in 
  position 
  are 
  vertical, 
  

  

  Mesopleurum, 
  The 
  episternum 
  in 
  the 
  Odouata 
  differs 
  remarkably 
  

   from 
  all 
  other 
  Pseudoneuroptera 
  and 
  indeed 
  from 
  all 
  other 
  insects, 
  only 
  

   the 
  Acrydii 
  approaching 
  them 
  in 
  the 
  enormously 
  long 
  and 
  large 
  epi- 
  

   sterna, 
  which 
  meet 
  in 
  front 
  to 
  form 
  a 
  large, 
  dorsal, 
  convex 
  area, 
  that 
  usu- 
  

   ally 
  occupied 
  in 
  other 
  insects 
  by 
  the 
  scutum. 
  The 
  epimerum 
  is 
  a 
  similar 
  

   piece, 
  and 
  nearly 
  as 
  large 
  as 
  the 
  lateral 
  portion 
  of 
  the 
  episternum 
  ; 
  it 
  

   is 
  in 
  Agrion 
  consolidated 
  with 
  the 
  meta-episternum. 
  In 
  Calopteryx, 
  

   however 
  (Fig. 
  6), 
  where 
  the 
  thorax 
  is 
  broader 
  and 
  higher, 
  the 
  two 
  scle- 
  

   rites 
  are 
  separate. 
  

  

  The 
  coxae 
  are 
  small, 
  conical; 
  the 
  trochantine 
  is 
  small, 
  triangular, 
  and 
  

   situated 
  directly 
  over 
  the 
  small 
  conical 
  coxa. 
  

  

  31etapleurum. 
  (Fig. 
  8.) 
  The 
  epistei^num 
  repeats 
  the 
  form 
  of 
  that 
  of 
  

   the 
  mesopleurum, 
  but 
  is 
  consolidated 
  with 
  the 
  meso-episternum. 
  The 
  

   episternum, 
  seen 
  laterally, 
  is 
  regularly 
  oblong, 
  and 
  three 
  times 
  as 
  long 
  

   as 
  broad. 
  

  

  The 
  trochantine 
  is 
  a 
  triangular 
  piece, 
  situated 
  directly 
  over 
  the 
  small 
  

   subconical 
  coxa. 
  

   In 
  Calopteryx 
  (Fig. 
  6) 
  the 
  meso-episternum 
  and 
  epimerum 
  are 
  much 
  

  

  