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  REPORT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

  

  III. 
  THE 
  DEVELOPMENT 
  OF 
  THE 
  BARK-BORINa 
  BEETLES 
  HYLUKGOPS 
  

  

  AND 
  XYLEBORUS. 
  

  

  Two 
  Scolytid 
  or 
  bark-boring 
  beetles 
  were 
  observed 
  in 
  abundance, 
  May 
  

   30, 
  1882, 
  near 
  Providence, 
  under 
  the 
  bark 
  of 
  wliite 
  pines 
  {Finns 
  strobus)^ 
  

   engaged 
  in 
  reproduction 
  and 
  egg-laying. 
  The 
  larger 
  of 
  these 
  was 
  Hy- 
  

   lurgops 
  pinifejo 
  Fitch 
  j 
  the 
  smaller 
  Xylehorus 
  cwlatus 
  Eich.^^ 
  Bringing 
  

   specimens 
  to 
  my 
  house, 
  the 
  next 
  day 
  I 
  was 
  able 
  to 
  observe 
  their 
  habits 
  

   more 
  closely. 
  The 
  following 
  notes 
  refer 
  entirely 
  to 
  X. 
  ccelatus. 
  The 
  

   female 
  was 
  in 
  her 
  hole, 
  the 
  end 
  of 
  her 
  abdomen 
  extending 
  straight 
  up 
  

   out 
  of 
  the 
  perpendicular 
  hole 
  or 
  ^'minej" 
  a 
  male 
  approached 
  her 
  and 
  

   rubbed 
  the 
  end 
  of 
  her 
  body 
  with 
  his 
  fore 
  pair 
  of 
  feet, 
  the 
  female 
  appar- 
  

   ently 
  responding 
  by 
  moving 
  back 
  and 
  forth 
  in 
  her 
  mine. 
  After 
  a 
  moment 
  

   or 
  two 
  the 
  male 
  visited 
  another 
  female 
  in 
  her 
  hole, 
  and 
  caressed 
  her 
  in 
  

   the 
  same 
  manner, 
  then 
  returned 
  to 
  the 
  first 
  female 
  and 
  inserted 
  his 
  intro- 
  

   mittent 
  organ 
  in 
  the 
  female, 
  the 
  end 
  of 
  whose 
  body 
  was 
  depressed, 
  so 
  as 
  

   to 
  leave 
  a 
  space 
  between 
  it 
  and 
  the 
  end 
  of 
  the 
  elytra. 
  Union 
  continued 
  

   for 
  six 
  minutes, 
  during 
  which 
  time 
  the 
  hindermost 
  pair 
  of 
  feet 
  of 
  the 
  

   male 
  kei)t 
  stroking 
  the 
  end 
  of 
  the 
  abdomen 
  of 
  its 
  mate, 
  while 
  its 
  anten- 
  

   u 
  86 
  were 
  vigorously 
  moving. 
  At 
  the 
  end- 
  of 
  this 
  time 
  it 
  immediately 
  

   withdrew 
  and 
  disappeared 
  down 
  another 
  hole, 
  the 
  female 
  descending 
  

   her 
  mine. 
  From 
  these 
  facts 
  we 
  infer 
  that 
  the 
  male 
  of 
  this 
  species 
  is 
  

   polygamous. 
  

  

  While 
  boring, 
  at 
  least 
  in 
  confinement, 
  the 
  borings 
  or 
  dust 
  is 
  thrown 
  

   out 
  around 
  the 
  mouth 
  of 
  the 
  mine 
  in 
  a 
  heap. 
  The 
  mine 
  or 
  tunnel 
  is 
  

   from 
  an 
  inch 
  to 
  an 
  inch 
  and 
  a 
  quarter 
  long; 
  at 
  close 
  intervals 
  on 
  one 
  

   side 
  there 
  are 
  lateral, 
  deep 
  notches 
  in 
  which 
  two 
  to 
  three 
  or 
  four 
  eggs 
  

   are 
  irregularly 
  laid; 
  or 
  the 
  eggs 
  are 
  carefully 
  deposited 
  side 
  by 
  side; 
  

   the 
  lateral 
  notches 
  are 
  then 
  filled 
  with 
  borings 
  or 
  dust 
  by 
  the 
  move- 
  

   ments 
  of 
  the 
  female 
  in 
  her 
  main 
  tunnel, 
  the 
  eggs 
  being 
  enclosed 
  in 
  the 
  

   mass 
  of 
  borings. 
  

  

  Hylurgops 
  does 
  not 
  make 
  lateral 
  notches, 
  but 
  places 
  her 
  eggs 
  side 
  

   by 
  side 
  in 
  a 
  single 
  recess 
  on 
  one 
  side 
  of 
  the 
  mine. 
  

  

  PI. 
  XXII, 
  Fig. 
  1, 
  represents 
  the 
  egg 
  of 
  the 
  Xyleborus 
  24 
  hours 
  after 
  

   impregnation. 
  The 
  primitive 
  band 
  {pb) 
  has 
  completely 
  formed, 
  as 
  well 
  

   as 
  the 
  serous 
  membrane; 
  the 
  primitive 
  band 
  lies 
  outside 
  of 
  the 
  yolk 
  

   and 
  at 
  this 
  time 
  the 
  segments 
  are 
  not 
  indicated. 
  

  

  Fig. 
  2 
  represents 
  another 
  egg 
  observed 
  June 
  1st. 
  The 
  segments 
  are 
  

   now 
  clearly 
  indicated, 
  and 
  those 
  of 
  the 
  head 
  (a^-a^) 
  are 
  as 
  clearly 
  indi- 
  

   cated 
  as 
  those 
  of 
  the 
  future 
  thorax 
  (a^-a"^) 
  or 
  those 
  of 
  the 
  abdomen 
  

   (1-8). 
  The 
  dotted 
  portion 
  represents 
  the 
  blastoderm, 
  while 
  the 
  clear 
  

   lobe-like 
  portions 
  are 
  the 
  appendages, 
  1-4 
  the 
  four 
  pair.-; 
  of 
  appendages 
  

   of 
  the 
  head, 
  and 
  I-III 
  the 
  three 
  pairs 
  of 
  legs. 
  The 
  amnion 
  (am) 
  or 
  in- 
  

   ner 
  membrane 
  is 
  now 
  entirely 
  formed 
  ; 
  the 
  cells 
  much 
  smaller 
  than 
  those 
  

   of 
  the 
  outer 
  or 
  serous 
  membrane 
  {ser). 
  

  

  134 
  1 
  am 
  indebted 
  to 
  tlie 
  kindness 
  of 
  Dr. 
  G. 
  H. 
  Horn 
  for 
  the 
  identification 
  of 
  tUis 
  species. 
  

  

  