﻿322 
  

  

  C. 
  STRICKLAND. 
  

  

  in 
  thickness 
  even 
  at 
  the 
  same 
  plane. 
  Likewise, 
  the 
  broadest 
  part 
  of 
  the 
  float 
  

   should 
  be 
  taken 
  for 
  comparative 
  tests. 
  The 
  frilled 
  cuticle 
  varies 
  in 
  thickness 
  when 
  

   seen 
  under 
  the 
  microscope, 
  possibly 
  owing 
  to 
  foreshortening 
  over 
  different 
  regions 
  

   of 
  the 
  egg, 
  being 
  especially 
  thick 
  at 
  the 
  prow 
  and 
  stern 
  points. 
  If 
  these 
  precautions 
  

   are 
  not 
  taken, 
  it 
  may 
  appear 
  that 
  two 
  species 
  have 
  different 
  characters 
  in 
  the 
  ova, 
  

   when 
  they 
  may 
  actually 
  be 
  similar. 
  

  

  It 
  may 
  be 
  mentioned 
  here 
  that 
  we 
  think 
  the 
  usual 
  statement 
  that 
  the 
  floats 
  of 
  

   the 
  egg 
  contain 
  air 
  is 
  not 
  correct. 
  What 
  seems 
  to 
  be 
  actually 
  the 
  case 
  is 
  that 
  the 
  

   frilled 
  cuticle, 
  as 
  well 
  as 
  the 
  floats, 
  merely 
  serve 
  to 
  attach 
  a 
  thin 
  film 
  of 
  air 
  on 
  their 
  

   surface 
  when 
  placed 
  dry 
  on 
  water. 
  When 
  in 
  the 
  egg-sac 
  the 
  eggs 
  are 
  immersed 
  

   in 
  the 
  body 
  fluids, 
  and 
  so 
  when 
  placed 
  in 
  water 
  the 
  water 
  can 
  permeate 
  directly 
  

   into 
  all 
  the 
  crannies 
  of 
  the 
  cuticle, 
  no 
  surface 
  film 
  of 
  air 
  forms, 
  and 
  the 
  egg 
  sinks. 
  

  

  We 
  found 
  the 
  eggs 
  of 
  the 
  two 
  species 
  indistinguishable 
  in 
  structure 
  and 
  of 
  

   practically 
  the 
  same 
  size. 
  The 
  length 
  of 
  the 
  opaque 
  portion 
  of 
  the 
  egg 
  was 
  the 
  

   same 
  in 
  both 
  cases, 
  the 
  floats 
  were 
  equally 
  broad 
  and 
  the 
  frills 
  of 
  the 
  float 
  similar 
  

   in 
  size, 
  and 
  the 
  frilled 
  cuticle 
  also 
  similar 
  in 
  both 
  cases 
  (fig. 
  1). 
  

  

  The 
  Larva. 
  

  

  In 
  both 
  species 
  we 
  observed 
  the 
  phenomenon 
  recorded 
  by 
  Stanton 
  (1911), 
  that 
  

   the 
  palmate 
  hairs 
  exist 
  at 
  first 
  as 
  merely 
  buds 
  which 
  finally 
  open 
  up. 
  The 
  leaflets 
  

   of 
  the 
  young 
  larva 
  are 
  always 
  more 
  cylindrical 
  than 
  those 
  of 
  the 
  older 
  specimens, 
  

   which 
  are 
  much 
  jagged 
  at 
  the 
  shoulder 
  just 
  below 
  the 
  origin 
  of 
  the 
  filament, 
  so 
  

   that 
  in 
  comparing 
  two 
  species 
  larvae 
  of 
  about 
  the 
  same 
  size 
  should 
  be 
  taken. 
  

   We 
  observe 
  the 
  following 
  differences 
  in 
  well-grown 
  larvae 
  : 
  — 
  

   1. 
  N. 
  rossi 
  has 
  its 
  frontal 
  hairs 
  as 
  described 
  by 
  Stanton 
  (fig. 
  2, 
  b) 
  ; 
  the 
  internal 
  

   anterior 
  hairs 
  are 
  excessively 
  long 
  and 
  filamentous 
  ; 
  the 
  external 
  anterior 
  rather 
  

   variable 
  in 
  length 
  in 
  different 
  individuals, 
  but 
  usually 
  not 
  much 
  more 
  than 
  a 
  

  

  a 
  ' 
  b 
  

  

  Fig. 
  2. 
  The 
  clypeal 
  hairs 
  of 
  full-grown 
  larvae 
  of 
  : 
  a, 
  Nyssomyzomyia 
  ludlowi 
  ; 
  b, 
  N. 
  rossi. 
  

  

  quarter 
  the 
  length 
  of 
  the 
  former 
  ; 
  while 
  the 
  posterior, 
  as 
  Stanton 
  first 
  pointed 
  out, 
  

   lie 
  considerably 
  within 
  the 
  anterior 
  internal, 
  projecting 
  over 
  the 
  clypeus. 
  On 
  the 
  

   other 
  hand, 
  in 
  ludlowi 
  the 
  anterior 
  internal 
  hairs 
  are 
  not 
  so 
  excessively 
  long 
  and 
  

  

  