﻿190 
  

  

  HUBERT 
  M. 
  MORRIS. 
  

  

  First 
  Stage 
  Larva 
  (newly 
  hatched). 
  

  

  The 
  newly 
  hatched 
  larva 
  (Plate 
  ix, 
  fig, 
  1) 
  is 
  about 
  1-05 
  mm. 
  long, 
  and 
  about 
  

   0-16 
  mm. 
  in 
  breadth. 
  The 
  length 
  of 
  the 
  head 
  is 
  0-15 
  mm. 
  The 
  latter 
  region 
  is 
  

   relatively 
  large, 
  of 
  a 
  pale 
  yellowish-brown 
  colour, 
  and 
  bears 
  several 
  long 
  setae. 
  

  

  The 
  body 
  is 
  colourless 
  and 
  transparent, 
  the 
  contents 
  of 
  the 
  alimentary 
  canal 
  

   showing 
  through 
  as 
  a 
  dark 
  median 
  line. 
  The 
  body 
  is 
  divided 
  into 
  12 
  segments, 
  

   each 
  bearing 
  several 
  short 
  and 
  rather 
  stout 
  setae, 
  arising 
  from 
  enlarged 
  conical 
  

   bases. 
  In 
  addition 
  to 
  these 
  there 
  are 
  a 
  great 
  number 
  of 
  smaller, 
  rather 
  conical 
  pro- 
  

   jections, 
  each 
  bearing 
  from 
  1-4 
  minute 
  spines, 
  these 
  structures 
  being 
  similar 
  

   in 
  appearance 
  to 
  the 
  scale-like 
  structures 
  of 
  the 
  fully 
  grown 
  larva. 
  

  

  The 
  larva 
  at 
  this 
  stage 
  bears 
  a 
  single 
  pair 
  of 
  spiracles, 
  which 
  is 
  situated 
  on 
  the 
  

   twelfth 
  segment, 
  in 
  a 
  position 
  similar 
  to 
  that 
  occupied 
  by 
  the 
  spiracles 
  of 
  that 
  segment 
  

   in 
  the 
  fully 
  grown 
  larva. 
  The 
  mouth-parts 
  do 
  not 
  show 
  any 
  very 
  marked 
  differences 
  

   from 
  those 
  of 
  the 
  adult 
  larva, 
  the 
  most 
  noticeable 
  being 
  the 
  presence 
  of 
  two 
  projections 
  

   between 
  those 
  at 
  the 
  anterior 
  end 
  of 
  the 
  labium, 
  whereas 
  only 
  one 
  occurs 
  in 
  the 
  fully 
  

   grown 
  larva. 
  

  

  Second 
  Stage 
  Larva. 
  

  

  In 
  this 
  stage 
  the 
  larva 
  is 
  about 
  2 
  mm. 
  in 
  length 
  and 
  about 
  0-22 
  mm. 
  in 
  breadth. 
  

   The 
  head 
  is 
  brown 
  and 
  shining, 
  and 
  bears 
  several 
  long 
  setae. 
  The 
  mouth-parts 
  are 
  

   similar 
  to 
  those 
  on 
  the 
  first 
  stage 
  larva 
  ; 
  the 
  median 
  anterior 
  processes 
  of 
  the 
  labium 
  

   are, 
  however, 
  rather 
  less 
  well 
  developed. 
  

  

  The 
  body 
  is 
  pale 
  brown 
  in 
  colour, 
  and 
  bears 
  short 
  stout 
  setae 
  and 
  spine-bearing 
  

   conical 
  scales 
  similar 
  to 
  those 
  of 
  the 
  first 
  stage 
  larva. 
  

  

  The 
  larva 
  in 
  this 
  stage 
  is 
  readily 
  distinguished 
  from 
  the 
  newly 
  hatched 
  larva, 
  in 
  

   addition 
  to 
  its 
  larger 
  size, 
  by 
  differences 
  in 
  the 
  tracheal 
  system. 
  The 
  second 
  stage 
  

   larva 
  is 
  amphipneustic, 
  having 
  a 
  pair 
  of 
  spiracles 
  situated 
  laterally 
  near 
  the 
  posterior 
  

   margin 
  of 
  the 
  first 
  body 
  segment, 
  and 
  a 
  second 
  pair 
  borne 
  more 
  dorsally, 
  in 
  a 
  position 
  

   similar 
  to 
  those 
  on 
  the 
  corresponding 
  segment 
  of 
  the 
  fully 
  grown 
  larva, 
  on 
  the 
  twelfth 
  

   segment. 
  The 
  spiracles 
  of 
  the 
  latter 
  pair 
  still 
  have 
  only 
  a 
  single 
  aperture. 
  There 
  is 
  

   no 
  indication, 
  in 
  this 
  stage, 
  of 
  the 
  stout 
  conical 
  processes 
  which 
  are 
  characteristic 
  of 
  

   the 
  fully 
  grown 
  larvae 
  of 
  this 
  family. 
  

  

  No 
  material 
  of 
  the 
  third 
  stage 
  larva 
  was 
  preserved. 
  

  

  Fourth 
  Stage 
  Larva 
  [fully 
  grown). 
  

  

  A 
  number 
  of 
  larvae 
  were 
  found 
  amongst 
  decaying 
  grass 
  on 
  27th 
  January, 
  and 
  on 
  

   the 
  next 
  day 
  some 
  of 
  them 
  were 
  observed 
  to 
  undergo 
  ecdysis. 
  When 
  fully 
  grown 
  

   the 
  larva 
  is 
  from 
  10-12 
  mm. 
  in 
  length, 
  and 
  about 
  1 
  -5 
  mm. 
  in 
  breadth. 
  The 
  length 
  

   of 
  the 
  head 
  is 
  about 
  1 
  mm. 
  (fig. 
  2). 
  

  

  Fig. 
  2. 
  Fully 
  grown 
  larva 
  of 
  Dilophus 
  febrilis, 
  X 
  18. 
  

  

  The 
  head 
  is 
  dark 
  brown 
  and 
  shining, 
  and 
  bears 
  several 
  long 
  setae. 
  The 
  mouth- 
  

   parts 
  and 
  antennae 
  (figs. 
  3-6) 
  do 
  not 
  show 
  any 
  very 
  marked 
  differences 
  from 
  those 
  

   of 
  other 
  Bibionid 
  larvae, 
  the 
  most 
  noticeable 
  being 
  the 
  presence 
  of 
  a 
  well 
  developed 
  

   median 
  projection 
  at 
  the 
  anterior 
  end 
  of 
  the 
  labium. 
  

  

  