﻿216 
  R. 
  J. 
  TILL 
  YARD. 
  

  

  the 
  prothoracic 
  spiracle 
  now 
  measures 
  0-1 
  mm., 
  while 
  that 
  of 
  the 
  first 
  abdominal 
  

   segment 
  measures 
  0-06 
  mm. 
  in 
  length, 
  the 
  breadths 
  being 
  about 
  two-thirds 
  of 
  these 
  

   measurements 
  in 
  each 
  case. 
  All 
  the 
  segments 
  show 
  a 
  new 
  development 
  of 
  fairly 
  

   numerous 
  secondary 
  setae 
  of 
  macrotrichial 
  type, 
  but 
  not 
  so 
  long 
  as 
  the 
  primary 
  

   setae. 
  On 
  the 
  pro- 
  and 
  mesothorax 
  these 
  setae 
  are 
  nearly 
  all 
  very 
  slender, 
  less 
  than 
  

   half 
  as 
  long 
  as 
  most 
  of 
  the 
  primarj' 
  setae 
  ; 
  the 
  pronotum 
  remains 
  shield-like 
  and 
  

   smooth, 
  without 
  any 
  microtrichia, 
  but 
  the 
  mesonotum 
  has 
  the 
  microtrichia 
  very 
  

   strongly 
  developed, 
  as 
  have, 
  all 
  the 
  succeeding 
  segments. 
  The 
  secondary 
  setae 
  on 
  

   abdominal 
  segments 
  2-8 
  are 
  slender 
  and 
  comparatively 
  short, 
  like 
  those 
  of 
  the 
  

  

  

  

  Fig. 
  6. 
  Ithone 
  fusca, 
  Newm., 
  second 
  

   larval 
  instar 
  ; 
  large 
  pinaculum 
  of 
  

   metathorax, 
  showing 
  invasion 
  of 
  

   secondary 
  setae 
  ( 
  x 
  112), 
  

  

  pronotum 
  ; 
  those 
  on 
  the 
  first 
  abdominal 
  segment 
  are 
  slightly 
  thicker, 
  and 
  those 
  on 
  

   the 
  metanotum 
  are 
  very 
  distinctly 
  thickened, 
  so 
  that 
  they 
  can 
  be 
  distinguished 
  at 
  a 
  

   glance 
  from 
  the 
  primary 
  setae, 
  which 
  remain 
  in 
  position. 
  The 
  invasion 
  of 
  these 
  

   setae 
  upon 
  and 
  around 
  the 
  large 
  pinaculum 
  of 
  the 
  metathorax, 
  which 
  encloses 
  the 
  

   four 
  primary 
  setae 
  gamma, 
  delta, 
  epsilon 
  and 
  rho, 
  is 
  shown 
  in 
  text-fig. 
  6. 
  

  

  Third 
  Larval 
  instar 
  (Plate 
  iv, 
  fig. 
  4; 
  text-fig. 
  7). 
  

  

  The 
  third 
  instar 
  is 
  again 
  considerably 
  larger 
  than 
  the 
  second, 
  but 
  owing 
  to 
  actual 
  

   differences 
  in 
  the 
  sizes 
  of 
  individual 
  larvae, 
  measurements 
  cannot 
  be 
  relied 
  upon 
  to 
  

   determine 
  the 
  correct 
  instar. 
  The 
  head 
  is 
  again 
  smaller 
  in 
  comparison 
  with 
  the 
  

   prothorax 
  than 
  in 
  the 
  second 
  instar, 
  and 
  the 
  turning-up 
  of 
  the 
  mouth-parts 
  is 
  

   distinctly 
  more 
  noticeable. 
  Antennae 
  and 
  labial 
  palpi 
  remain 
  five-segmented. 
  The 
  

   spiracles 
  are 
  now 
  very 
  oval 
  in 
  shape, 
  the 
  prothoracic 
  spiracle 
  measuring 
  0-16 
  mm., 
  

   and 
  being 
  only 
  half 
  as 
  broad 
  as 
  long, 
  while 
  the 
  first 
  abdominal 
  spiracle 
  is 
  0-10 
  mm. 
  

   long, 
  and 
  a 
  little 
  more 
  than 
  half 
  as 
  broad. 
  Transverse 
  striation 
  of 
  the 
  lips 
  of 
  the 
  

   spiracle 
  and 
  of 
  its 
  internal 
  opening 
  is 
  now 
  apparent. 
  The 
  most 
  noticeable 
  change 
  

   in 
  this 
  instar 
  is 
  the 
  very 
  large 
  invasion 
  of 
  secondary 
  setae 
  on 
  all 
  the 
  segments 
  ; 
  the 
  

  

  