﻿WAGNER 
  ON 
  THE 
  HESSIAN 
  FLY. 
  [13] 
  

  

  hairs, 
  attaining 
  on 
  the 
  edge 
  of 
  the 
  wing 
  their 
  greatest 
  length, 
  and 
  which, 
  

   like 
  the 
  hairs 
  of 
  the 
  wing 
  disk, 
  are 
  easily 
  rubbed. 
  Each 
  wing 
  is 
  fur- 
  

   nished 
  with 
  three 
  longitudinal 
  veins, 
  the 
  first 
  of 
  which 
  is 
  near 
  the 
  ante- 
  

   rior 
  marginal 
  vein, 
  first 
  running 
  parallel 
  with 
  the 
  latter, 
  uniting 
  with 
  it 
  

   near 
  the 
  middle 
  of 
  the 
  anterior 
  margin. 
  The 
  second 
  longitudinal 
  vein 
  

   rises 
  straight 
  upward, 
  curves 
  considerably 
  in 
  a 
  posterior 
  direction 
  near 
  

   its 
  last 
  third, 
  ending 
  yet 
  a 
  little 
  before 
  the 
  tip 
  of 
  the 
  wing. 
  Finally, 
  the 
  

   third 
  longitudinal 
  vein, 
  which 
  in 
  its 
  lower 
  half 
  is 
  more 
  prominent 
  than 
  the 
  

   first 
  two, 
  arises 
  from 
  the 
  same 
  root 
  as 
  the 
  second, 
  but 
  strongly 
  diverges 
  

   from 
  it. 
  Just 
  opposite 
  the 
  end 
  (Mlindung) 
  of 
  the 
  first 
  longitudinal 
  vein 
  

   it 
  divides 
  into 
  two 
  branches, 
  of 
  which 
  one 
  runs 
  in 
  an 
  obtuse 
  angle 
  to 
  

   the 
  posterior 
  margin, 
  while 
  the 
  other 
  reaches 
  the 
  margin 
  nearly 
  in 
  

   the 
  middle 
  between 
  the 
  end 
  of 
  the 
  preceding 
  branch 
  and 
  the 
  second 
  

   longitudinal 
  vein. 
  Both 
  longitudinal 
  veins 
  are 
  connected 
  with 
  each 
  

   other 
  by 
  a 
  very 
  pale 
  transverse 
  vein, 
  which, 
  directed 
  from 
  the 
  posterior 
  

   toward 
  the 
  anterior 
  and 
  inner 
  side, 
  meets 
  the 
  first 
  longitudinal 
  vein 
  at 
  

   half 
  the 
  distance 
  of 
  its 
  end 
  from 
  the 
  roots 
  of 
  the 
  wing. 
  This 
  is 
  the 
  

   only 
  transverse 
  vein 
  in 
  the 
  wing, 
  and 
  is 
  difficult 
  to 
  see. 
  I 
  succeeded 
  

   best 
  in 
  finding 
  it 
  by 
  placing 
  the 
  insect 
  on 
  its 
  back, 
  fastening 
  the 
  wing- 
  

   tips 
  in 
  such 
  a 
  manner 
  that 
  they 
  somewhat 
  rose 
  inwardly. 
  The 
  trans- 
  

   verse 
  vein 
  of 
  the 
  wing 
  directed 
  toward 
  the 
  entering 
  light 
  can 
  then 
  be 
  

   seen 
  by 
  reflected 
  Ught. 
  A 
  magnifying 
  power 
  of 
  seventy 
  sufficed, 
  while 
  

   a 
  power 
  of 
  even 
  four 
  hundred 
  did 
  not 
  show 
  it 
  when 
  the 
  wing 
  was 
  kept 
  

   in 
  a 
  horizontal 
  position. 
  A 
  fold 
  traversing 
  the 
  whole 
  wing 
  immedi- 
  

   ately 
  before 
  the 
  third 
  longitudinal 
  vein 
  and 
  its 
  anterior 
  corners 
  is 
  very 
  

   characteristic. 
  The 
  comparatively 
  long 
  halteres 
  are 
  light 
  brown. 
  They 
  

   and 
  the 
  long, 
  slender, 
  more 
  dirty 
  light-brown 
  legs 
  are 
  covered 
  with 
  

   closely 
  appressed,^ 
  scale-like 
  hairs, 
  the 
  latter 
  being 
  very 
  regularly 
  paral- 
  

   lelly 
  transversely 
  striped. 
  Coxa 
  cylindrical, 
  trochanter 
  (Schenkelring) 
  

   nearly 
  globular, 
  both 
  of 
  the 
  color 
  of 
  the 
  abdomen. 
  Terminal 
  spurs 
  not 
  

   present 
  on 
  the 
  tibia. 
  Of 
  the 
  five 
  tarsal 
  joints 
  the 
  first 
  is 
  the 
  shortest 
  ; 
  

   their 
  proportional 
  length 
  is 
  approximately 
  reached 
  by 
  1 
  : 
  12, 
  5 
  : 
  4, 
  2 
  : 
  2, 
  7 
  : 
  

   1, 
  3. 
  The 
  terminal 
  joint 
  bears 
  two 
  hair-like, 
  coal-black 
  claws, 
  beneath 
  

   which 
  is 
  but 
  one 
  disk-like, 
  haired 
  cushion. 
  The 
  cylindrical, 
  sparsely 
  

   haired 
  abdomen 
  consists 
  of 
  nine 
  segments, 
  of 
  which 
  the 
  last, 
  very 
  minute, 
  

   is 
  of 
  yellow-brown 
  color, 
  posteriorly 
  bearing 
  the 
  dark-red 
  clasper. 
  The 
  

   eighth 
  segment 
  is 
  smaller 
  than 
  the 
  preceding, 
  equally 
  large 
  segments. 
  

   Each 
  of 
  the 
  two 
  clasper-halves 
  consists 
  of 
  two 
  joints: 
  the 
  thicker 
  basal 
  

   joint 
  is 
  not 
  haired 
  on 
  its 
  inner 
  side; 
  on 
  its 
  outer 
  side 
  are 
  three 
  shallow 
  

   transverse 
  grooves; 
  the 
  longer 
  terminal 
  joint 
  is 
  strongly 
  curved 
  inward. 
  

   Between 
  the 
  claspers 
  are 
  two 
  pale-brown 
  conical 
  papillae, 
  densely 
  beset 
  

   with 
  short 
  hairs, 
  which, 
  as 
  I 
  believe 
  I 
  have 
  observed, 
  act 
  together 
  with 
  

   the 
  unpaired 
  organ 
  mentioned 
  above 
  as 
  an 
  auxiliary 
  copulatory 
  organ. 
  

   Female. 
  (Fig. 
  18.) 
  — 
  The 
  length 
  from 
  the 
  front 
  to 
  the 
  end 
  of 
  the 
  pro- 
  

   truded 
  ovipositor 
  varies 
  between 
  2.5°^™ 
  and 
  3.5"^°^, 
  and 
  is 
  therefore 
  less 
  

   constant 
  than 
  in 
  the 
  male. 
  Black 
  is 
  here 
  also 
  the 
  predominating 
  color 
  

   of 
  the 
  body, 
  being 
  even 
  more 
  intense, 
  shiny 
  velvet-black. 
  Nearly 
  the 
  

   whole 
  abdomen, 
  the 
  sutures 
  between 
  the 
  abdominal 
  segments, 
  and 
  the 
  

   median 
  dorsal 
  line 
  of 
  the 
  abdomen 
  are 
  raspberry-red 
  ; 
  the 
  base 
  of 
  antennbe 
  

   and 
  their 
  place 
  of 
  insertion 
  are 
  often 
  blood-red. 
  On 
  the 
  ventral 
  side 
  of 
  

   each 
  of 
  the 
  six 
  abdominal 
  segments 
  we 
  notice 
  here, 
  better 
  than 
  in 
  the 
  

   male, 
  a 
  nearly 
  quadrate 
  velvet-black 
  spot, 
  which, 
  however, 
  soon 
  after 
  

   death 
  loses 
  its 
  distinct 
  margin, 
  the 
  whole 
  ventral 
  then 
  assuming 
  the 
  

   color 
  of 
  the 
  dorsal 
  side. 
  The 
  pilosity 
  of 
  all 
  body-parts 
  is 
  black 
  ; 
  the 
  

   antennae 
  are 
  reddish-yellow; 
  the 
  latter 
  are 
  one-third 
  of 
  the 
  body 
  -length; 
  

  

  