﻿WAGNER 
  ON 
  THE 
  HESSIAN 
  FLY. 
  [15] 
  

  

  h— 
  The 
  egg. 
  (Fig. 
  1, 
  2.) 
  

  

  I 
  have 
  observed 
  the 
  act 
  of 
  copulation 
  in 
  our 
  gall-gnat 
  several 
  times. 
  

   On 
  the 
  6th 
  of 
  September 
  I 
  brought 
  to 
  a 
  female, 
  hatched 
  early 
  in 
  the 
  

   morniug 
  of 
  the 
  same 
  day, 
  a 
  male. 
  The 
  female 
  sat 
  quietly 
  on 
  the 
  wall 
  

   of 
  the 
  cage 
  and 
  soon 
  retracted 
  the 
  protruding 
  ovipositor 
  up 
  to 
  near 
  the 
  

   terminal 
  joint. 
  After 
  the 
  male 
  had 
  flown 
  for 
  a 
  while 
  around 
  the 
  female, 
  

   he 
  alighted 
  on 
  her, 
  bending 
  his 
  abdomen 
  downwards, 
  embracing 
  the 
  ovi- 
  

   positor 
  with 
  his 
  claspers, 
  thus 
  reaching 
  its 
  orifice 
  from 
  below. 
  Copula- 
  

   tion 
  was 
  repeated 
  in 
  short 
  intervals, 
  each 
  lasting 
  from 
  one 
  to 
  two 
  minutes. 
  

   After 
  this 
  the 
  male 
  was 
  captured 
  and 
  a 
  tender 
  wheat 
  sprout 
  just 
  taken 
  

   from 
  the 
  soil 
  was 
  placed 
  to 
  the 
  female. 
  After 
  a 
  good 
  half 
  hour 
  the 
  fly 
  

   ascended 
  on 
  the 
  introduced 
  plant 
  and 
  deposited 
  eggs 
  on 
  the 
  surface 
  of 
  

   several 
  leaves. 
  With 
  the 
  head 
  directed 
  toward 
  the 
  tip 
  of 
  the 
  leaf, 
  she 
  

   slowly 
  walked 
  diagonally 
  up, 
  after 
  each 
  short 
  pause 
  depositing 
  two 
  

   eggs 
  between 
  the 
  intervening 
  spaces 
  of 
  two 
  successive 
  longitudinal 
  leaf- 
  

   veins, 
  so 
  that, 
  though 
  the 
  eggs 
  were 
  placed 
  in 
  a 
  parallel 
  position, 
  one 
  of 
  

   them 
  was 
  a 
  little 
  ahead 
  of 
  the 
  other. 
  It 
  could 
  be 
  distinctly 
  ob- 
  

   served 
  during 
  the 
  act 
  how 
  the 
  egg 
  each 
  time 
  was 
  expressed 
  by 
  the 
  ovi- 
  

   positor. 
  After 
  removal 
  of 
  the 
  plant 
  a 
  few 
  others 
  were 
  substituted^ 
  

   which 
  were 
  likewise 
  beset 
  with 
  eggs 
  by 
  the 
  insect, 
  wherein, 
  although 
  the 
  

   piocess 
  was 
  analogous, 
  a 
  deposition 
  of 
  eggs 
  in 
  pairs 
  did 
  not 
  always 
  oc- 
  

   cur. 
  In 
  all 
  I 
  counted 
  83 
  eggs 
  deposited 
  by 
  the 
  female. 
  

  

  In 
  all 
  cases 
  observed 
  the 
  number 
  of 
  eggs 
  deposited 
  by 
  one 
  female 
  

   were 
  more 
  than 
  80 
  and 
  less 
  than 
  100. 
  I 
  reached 
  this 
  result 
  either 
  by 
  

   placing 
  sprouts 
  under 
  the 
  glass 
  globe, 
  as 
  long 
  as 
  any 
  eggs 
  were 
  depos- 
  

   ited, 
  or, 
  instead, 
  a 
  whole 
  bunch 
  of 
  sprouts, 
  prepared 
  for 
  it 
  in 
  a 
  flower- 
  

   pot, 
  was 
  covered 
  with 
  a 
  glass 
  globe 
  and 
  the 
  fertilized 
  female 
  introduced.* 
  

   After 
  the 
  fly 
  has 
  attended 
  to 
  the 
  care 
  of 
  her 
  off*si)ring5 
  death 
  follows 
  

   both 
  sexes 
  within 
  a 
  few 
  hours. 
  

  

  The 
  egg 
  has 
  a 
  length 
  of 
  0.3°^™ 
  and 
  a 
  diameter 
  of 
  0.08™™ 
  ; 
  it 
  is 
  cylin- 
  

   drical, 
  rounded 
  on 
  both 
  ends, 
  smooth, 
  transparent, 
  yexj 
  faintly 
  light 
  

   brown 
  or 
  furnished 
  with 
  several 
  red 
  dots, 
  which 
  are 
  often 
  confluent 
  to 
  

   a 
  single 
  dot, 
  disappearing 
  in 
  a 
  few 
  hours, 
  permanently 
  changing 
  color 
  

   into 
  brown 
  red. 
  

  

  If 
  we 
  hold 
  the 
  leaves 
  on 
  which 
  our 
  gall-gnat 
  has 
  deposited 
  eggs 
  to 
  the 
  

   light 
  the 
  latter 
  become 
  conspicuous 
  by 
  a 
  red, 
  silken 
  hue 
  ; 
  but 
  if 
  the 
  

   hatching 
  of 
  the 
  maggots 
  has 
  already 
  taken 
  place, 
  we 
  notice 
  in 
  the 
  small 
  

   valleys 
  between 
  the 
  longitudinal 
  nerves 
  small 
  excavations 
  j 
  the 
  former 
  

   position 
  of 
  the 
  ovules 
  and 
  the 
  remaining 
  egg-skins 
  appear 
  as 
  elongate 
  

   white 
  dots. 
  

  

  Owing 
  to 
  the 
  very 
  minute 
  size 
  of 
  the 
  eggs 
  their 
  gathering 
  in 
  the 
  field 
  

   is 
  very 
  difiicult 
  even 
  to 
  an 
  experienced 
  eye. 
  A.n 
  examination 
  of 
  the 
  leaves 
  

   with 
  the 
  magnifying 
  glass 
  requires 
  much 
  patience 
  and 
  endurance. 
  I 
  

   therefore 
  preferred, 
  with 
  a 
  view 
  of 
  finding 
  eggs, 
  to 
  examine 
  a 
  larger 
  quan- 
  

   tity 
  of 
  sprouts 
  of 
  a 
  field, 
  in 
  whose 
  neighborhood 
  the 
  fly 
  formerly 
  occurred 
  

   in 
  multitudes, 
  and 
  have 
  in 
  this 
  case 
  not 
  only 
  easily 
  found 
  them, 
  but 
  have 
  

   also 
  found 
  their 
  arrangement 
  to 
  correspond 
  with 
  what 
  has 
  been 
  stated 
  

   above. 
  

  

  As 
  to 
  the 
  length 
  of 
  time 
  from 
  the 
  deposition 
  of 
  the 
  egg 
  up 
  to 
  the 
  

   hatching 
  of 
  the 
  maggot 
  I 
  can 
  communicate 
  some 
  observations. 
  Those 
  

  

  * 
  Several 
  difficulties 
  occur 
  in 
  the 
  rearing 
  of 
  mapgots 
  from 
  eggs, 
  which 
  lie 
  principally 
  partly 
  

   in 
  the 
  great 
  teudernoss, 
  and 
  there 
  fore 
  easy 
  vulnerability 
  of 
  all 
  the 
  parts 
  of 
  our 
  fly, 
  partly 
  also 
  

   in 
  the 
  less 
  frequent 
  occurrence 
  of 
  the 
  male. 
  Aside 
  from 
  the 
  pilosity, 
  each 
  laceration 
  of 
  the 
  insect 
  

   foils 
  the 
  experiment 
  to 
  produce 
  copulation. 
  Therefore 
  it 
  requires 
  great 
  care, 
  in 
  capturing 
  espoei- 
  

   ally, 
  since 
  the 
  legs 
  especially 
  thereby 
  receive 
  injury. 
  Furthermore 
  young 
  females 
  obstinately 
  I'esist 
  all 
  

   invitations 
  of 
  concupiscent 
  males 
  and 
  the 
  reveise. 
  For 
  the 
  success 
  of 
  the 
  experiment, 
  therefore, 
  un- 
  

   injured, 
  fully 
  colored 
  individuals 
  of 
  both 
  sexes 
  are 
  the 
  essential 
  requirements. 
  

  

  