﻿6 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL. 
  MUSEUM 
  vol. 
  G7 
  

  

  distinguishing 
  between 
  groups 
  of 
  species, 
  when 
  supported 
  by 
  other 
  

   characters. 
  Usually 
  the 
  mesonotal 
  pubescence 
  is 
  restricted 
  to 
  the 
  

   parapsidal 
  grooves 
  and 
  the 
  space 
  behind 
  the 
  middle 
  lobe, 
  but 
  in 
  a 
  

   few 
  species 
  pubescence 
  arises 
  over 
  the 
  entire 
  surface 
  of 
  the 
  lobes 
  

   as 
  well 
  as 
  from 
  the 
  parapsidal 
  furrows; 
  this 
  character 
  appears 
  to 
  

   be 
  very 
  constant 
  within 
  species. 
  The 
  length 
  of 
  the 
  head 
  antero-pos- 
  

   teriorly 
  is 
  relatively 
  constant, 
  and 
  in 
  the 
  small 
  number 
  of 
  cases 
  

   where 
  the 
  difference 
  between 
  species 
  is 
  sufficient 
  to 
  permit 
  the 
  em- 
  

   ployment 
  of 
  this 
  character, 
  it 
  is 
  good. 
  The 
  length 
  of 
  the 
  malar 
  space, 
  

   the 
  number 
  and 
  the 
  relative 
  length 
  of 
  the 
  antennal 
  segments 
  have 
  

   considerable 
  value, 
  but 
  again, 
  must 
  be 
  used 
  with 
  care 
  and 
  supported 
  

   by 
  other 
  characters. 
  Wing 
  venation, 
  particularly 
  the 
  length 
  of 
  the 
  

   second 
  abscissa 
  of 
  radius 
  as 
  compared 
  with 
  the 
  first 
  and 
  third 
  

   abscissae 
  and 
  with 
  the 
  first 
  intercubitus, 
  the 
  relative 
  length 
  also 
  of 
  

   that 
  part 
  of 
  cubitus 
  which 
  lies 
  between 
  the 
  recurrent 
  and 
  the 
  first 
  

   intercubitus, 
  and 
  the 
  length 
  of 
  the 
  radial 
  cell, 
  which 
  is 
  dependent 
  

   on 
  the 
  point 
  where 
  radius 
  attains 
  the 
  wing 
  margin, 
  will 
  be 
  found 
  

   very 
  helpful, 
  but 
  within 
  limits. 
  It 
  will 
  be 
  seen 
  from 
  this 
  brief 
  

   discussion 
  that 
  variability 
  is 
  so 
  pronounced 
  in 
  species 
  of 
  Micro- 
  

   bracon 
  that 
  determinations 
  should 
  be 
  made 
  only 
  after 
  a 
  very 
  careful 
  

   weighing 
  of 
  all 
  points. 
  It 
  is 
  hoped 
  that 
  the 
  following 
  key 
  together 
  

   with 
  the 
  notes 
  found 
  in 
  the 
  text 
  will 
  aid 
  considerably 
  in 
  making 
  

   such 
  determinations. 
  Unfortunately 
  it 
  was 
  found 
  necessary 
  to 
  clas- 
  

   sify 
  the 
  females 
  and 
  males 
  separately 
  beyond 
  the 
  thirteenth 
  couplet. 
  

   By 
  doing 
  this 
  it 
  has 
  been 
  possible 
  to 
  present 
  a 
  key 
  to 
  the 
  females 
  

   which 
  will 
  probably 
  be 
  found 
  quite 
  satisfactory; 
  while 
  if 
  the 
  

   males 
  had 
  been 
  incorporated 
  the 
  fullest 
  use 
  could 
  not 
  have 
  been 
  

   made 
  of 
  the 
  variations 
  in 
  the 
  length 
  of 
  the 
  ovipositor 
  sheaths 
  between 
  

   different 
  species, 
  one 
  of 
  the 
  most 
  valuable 
  characters. 
  Any 
  key 
  to 
  

   the 
  males 
  of 
  Microbracon 
  must, 
  it 
  seems 
  to 
  me, 
  be 
  rather 
  unsat- 
  

   isfactory, 
  because 
  of 
  the 
  apparently 
  complete 
  intergradation 
  of 
  

   species. 
  The 
  one 
  here 
  given 
  will, 
  however, 
  probably 
  serve 
  to 
  identify 
  

   the 
  normal 
  males. 
  The 
  identity 
  of 
  those 
  which 
  represent 
  the 
  ex- 
  

   tremes 
  in 
  variation 
  must 
  often 
  be 
  left 
  in 
  doubt 
  unless 
  they 
  can 
  be 
  

   connected 
  by 
  biological 
  records 
  with 
  females 
  or 
  more 
  normal 
  males. 
  

   In 
  the 
  following 
  table 
  66 
  species 
  are 
  included 
  in 
  the 
  female 
  key 
  and 
  

   73 
  species 
  in 
  the 
  male 
  key; 
  seven 
  species 
  which 
  are 
  known 
  only 
  in 
  

   the 
  male 
  sex, 
  and 
  in 
  all 
  cases 
  but 
  one 
  based 
  upon 
  a 
  single 
  specimen, 
  

   can 
  not 
  be 
  placed 
  in 
  the 
  female 
  key 
  because 
  of 
  the 
  necessity 
  of 
  mak- 
  

   ing 
  much 
  use 
  of 
  the 
  relative 
  length 
  of 
  the 
  ovipositor 
  sheaths 
  in 
  this 
  

   part 
  of 
  the 
  table. 
  Some 
  other 
  species 
  are 
  known 
  only 
  from 
  female 
  

   specimens, 
  and 
  in 
  these 
  cases 
  the 
  position 
  assigned 
  in 
  the 
  male 
  key 
  

   was 
  determined 
  by 
  characters 
  exhibited 
  by 
  the 
  females, 
  after 
  making 
  

  

  