﻿748 
  REPORT 
  UNITED 
  STATES 
  GEOLOGICAL 
  SURVEY. 
  

  

  nearly 
  1,000 
  species 
  (!), 
  swarm 
  even 
  in 
  our 
  houses, 
  especially 
  in 
  the 
  coun- 
  

   try, 
  where 
  in 
  October 
  and 
  November 
  I 
  have 
  seen 
  immense 
  numbers 
  in- 
  

   side 
  of 
  the 
  windows, 
  and 
  I 
  believe 
  that 
  they 
  hibernate 
  behind 
  the 
  shut- 
  

   ters, 
  in 
  the 
  curtains," 
  etc. 
  

   Were 
  it 
  not 
  for 
  the 
  native 
  ichneumon 
  parasite, 
  (Fig. 
  IG, 
  a, 
  male; 
  b, 
  

  

  female,) 
  which 
  has 
  been 
  found 
  to 
  prey 
  upon 
  

   it 
  very 
  extensively, 
  the 
  cultivation 
  of 
  the 
  

   cabbage 
  would 
  have 
  to 
  be 
  given 
  up 
  in 
  some 
  

   districts. 
  This 
  invaluable 
  ichneumon 
  is 
  one 
  

   of 
  the 
  chalcid 
  family, 
  and 
  is 
  the 
  Fterom- 
  

   alus 
  puparuni 
  of 
  Linnaeus. 
  It 
  is 
  well 
  known 
  

   that 
  the 
  cabbage-caterpillar 
  (Ple'>^i<i 
  rapce) 
  

   was 
  introduced 
  into 
  this 
  country 
  about 
  the 
  

   year 
  1857. 
  I 
  had 
  supposed 
  that 
  the 
  par- 
  

   asite 
  had 
  perhaps 
  been 
  imported 
  with 
  its 
  

   host, 
  but 
  now 
  find 
  that 
  it 
  is 
  undoubtedly 
  a 
  

   native 
  of 
  this 
  country 
  as 
  well 
  as 
  Europe, 
  j 
  

   Having 
  been 
  favored 
  by 
  Mr. 
  Francis 
  Walker 
  

   with 
  specimens 
  of 
  both 
  sexes 
  from 
  England, 
  

   labeled 
  by 
  him 
  Pt. 
  puparum, 
  I 
  found 
  that 
  

   our 
  specimens 
  did 
  not 
  differ 
  specificially. 
  

   Further, 
  Mr. 
  Walker 
  wrote 
  me 
  that 
  there 
  

   Fig. 
  16.— 
  Parasite 
  of 
  the 
  im- 
  were 
  specimens 
  of 
  the 
  same 
  species 
  in 
  

   ported 
  Cabbage 
  Butterfly. 
  the 
  British 
  Museum, 
  taken 
  in 
  Hudson's 
  

   Bay 
  territory 
  in 
  1844. 
  During 
  the 
  past 
  summer 
  Mr. 
  P. 
  S. 
  Sprague, 
  

   sent 
  me 
  specimens 
  which 
  had 
  been 
  raised 
  from 
  the 
  rape 
  caterpillar 
  in 
  

   Vermont. 
  Mr. 
  J. 
  A. 
  Lintner 
  has 
  also 
  published 
  a 
  note 
  in 
  the 
  Ameri- 
  

   can 
  Naturalist 
  stating 
  that 
  he 
  had 
  reared 
  this 
  parasite 
  from 
  the 
  same 
  

   kind 
  of 
  caterpillar, 
  and 
  previously 
  to 
  this 
  Mr. 
  S. 
  H. 
  Scudder 
  had 
  re- 
  

   ceived 
  numerous 
  specimens 
  from 
  Mr. 
  A. 
  G. 
  T. 
  Eitchie, 
  of 
  Montreal, 
  

   Canada, 
  who, 
  if 
  1 
  understand 
  his 
  letter 
  aright, 
  first 
  observed 
  these 
  

   chalcids 
  upon 
  the 
  cabbage-leaves 
  in 
  July, 
  1870, 
  when 
  the 
  caterpillars 
  

   were 
  abundant. 
  On 
  the 
  23d 
  of 
  August 
  of 
  the 
  same 
  year 
  he 
  had 
  some 
  

   of 
  the 
  parasites 
  hatch 
  out. 
  To 
  Mr. 
  Ritchie, 
  then, 
  is 
  due 
  the 
  credit 
  of 
  

   being 
  the 
  first 
  to 
  make 
  known 
  the 
  history 
  of 
  this 
  invaluable 
  insect. 
  

  

  It 
  seems 
  that 
  the 
  parasite 
  covers 
  even 
  a 
  wider 
  field 
  than 
  its 
  host, 
  and 
  

   probably 
  preys 
  on 
  our 
  native 
  cabbage-butterfly, 
  the 
  Pieris 
  oleracea, 
  as 
  

   in 
  Europe 
  it 
  preys 
  on 
  Pieris 
  hrassicce, 
  the 
  caterpillar 
  so 
  destructive 
  to 
  

   the 
  cabbage 
  there. 
  

  

  Description. 
  — 
  The 
  male 
  of 
  this 
  Pteromalus 
  is 
  a 
  beautiful 
  pale-green 
  fly, 
  with 
  the 
  

   body 
  finely 
  punctured 
  and 
  emitting 
  metallic 
  tints 
  ; 
  the 
  abdomen, 
  or 
  hind 
  l)ody, 
  is 
  flat, 
  

   in 
  dried 
  specimens 
  with 
  a 
  deep 
  crease 
  along 
  the 
  middle 
  of 
  the 
  upper 
  side, 
  and 
  it 
  is 
  

   much 
  lighter 
  in 
  color 
  and 
  with 
  more 
  decided 
  metallic 
  reflections 
  than 
  in 
  the 
  rest 
  of 
  

   the 
  body. 
  The 
  antenn;© 
  are 
  honey-yellow, 
  with 
  narrow 
  black 
  wings. 
  The 
  legs 
  are 
  

   pale 
  honey-yellow. 
  It 
  is 
  .08 
  inch 
  to 
  a 
  tenth 
  in 
  length. 
  

  

  Tlie 
  body 
  of 
  the 
  female, 
  which 
  would 
  be 
  thought 
  at 
  first 
  to 
  be 
  an 
  entirely 
  different 
  

   kind 
  of 
  insect, 
  is 
  much 
  stoutei", 
  broader, 
  with 
  a 
  broader 
  oval 
  abdomen, 
  ending 
  m 
  a 
  very 
  

   short 
  ovipositor, 
  while 
  the 
  under 
  side 
  of 
  tlie 
  body 
  near 
  the 
  base 
  has 
  a 
  large 
  conical 
  

   projection. 
  It 
  is 
  much 
  duller 
  green 
  than 
  the 
  male, 
  and 
  the 
  body 
  is 
  more 
  coarsely 
  

   punctured. 
  The 
  scutellum 
  of 
  the 
  metathorax 
  is 
  regularly 
  convex, 
  not 
  keeled, 
  in 
  both 
  

   sexes. 
  The 
  antennas 
  are 
  brown, 
  and 
  the 
  legs 
  brown, 
  becoming 
  pale 
  toward 
  the 
  ends, 
  

   the 
  ends 
  of 
  the 
  femora 
  being 
  pale 
  ; 
  the 
  tibite 
  pale 
  brown 
  in 
  the 
  middle, 
  much 
  paler 
  at 
  

   each 
  end, 
  while 
  the 
  tarsi 
  are 
  whitish, 
  though 
  the 
  tip 
  of 
  the 
  last 
  joint 
  is 
  durk. 
  It 
  is 
  

   from 
  a 
  line 
  to 
  a 
  line 
  and 
  a 
  third 
  in 
  length. 
  It 
  differs 
  from 
  Harris's 
  Pteromalus 
  vanessw 
  

   in 
  the 
  little 
  pipco 
  known 
  as 
  the 
  scutellum 
  of 
  the 
  metathorax 
  being 
  smooth, 
  not 
  keeled, 
  

   and 
  by 
  its 
  darker 
  legs. 
  

  

  The 
  larva 
  is 
  a 
  little 
  white 
  maggot 
  about 
  a 
  sixth 
  (.17) 
  of 
  an 
  inch 
  in 
  length. 
  The 
  

   body 
  consists 
  of 
  thirteen 
  segments, 
  exclusive 
  of 
  the 
  head, 
  and 
  is 
  cylindrical, 
  taper- 
  

   ing 
  rapidly 
  toward 
  the 
  head, 
  while 
  the 
  end 
  of 
  the 
  body 
  is 
  acutely 
  pointed. 
  The 
  

   chrysalis 
  is 
  whitish, 
  the 
  limbs 
  being 
  folded 
  along 
  the 
  under 
  side 
  of 
  the 
  body, 
  the 
  

  

  