﻿189 
  

  

  THE 
  LARVAL 
  AND 
  PUPAL 
  STAGES 
  OF 
  THE 
  BIBIONIDAE.— 
  PART 
  II. 
  

  

  By 
  Hubert 
  M. 
  Morris, 
  M.Sc, 
  F.E.S. 
  

  

  Entomological 
  Department, 
  Institute 
  of 
  Plant 
  Pathology, 
  

   Rothamsted 
  Experimental 
  Station, 
  Harpenden. 
  

  

  (Plate 
  IX.) 
  

  

  In 
  previous 
  papers 
  (1917,1921) 
  accounts 
  have 
  been 
  given 
  of 
  four 
  species 
  of 
  the 
  

   genus 
  Bibio, 
  and 
  the 
  present 
  paper 
  deals 
  with 
  two 
  species 
  of 
  the 
  genus 
  Dilophus, 
  

   viz., 
  D. 
  febrilis, 
  L., 
  and 
  D. 
  albipennis, 
  Mg. 
  They 
  are 
  the 
  commonest 
  species 
  of 
  

   Dilophus 
  in 
  Britain, 
  and 
  both 
  frequently 
  occur 
  in 
  great 
  numbers. 
  

  

  Dilophus 
  febrilis 
  has 
  often 
  been 
  recorded 
  as 
  causing 
  damage 
  to 
  the 
  roots 
  of 
  plants, 
  

   especially 
  hops, 
  in 
  the 
  larval 
  state. 
  This 
  species 
  may 
  be 
  double-brooded, 
  adults 
  

   appearing 
  in 
  May, 
  and 
  again 
  in 
  smaller 
  numbers 
  in 
  August 
  and 
  September. 
  D. 
  albi- 
  

   pennis 
  appears 
  to 
  have 
  only 
  a 
  single 
  brood, 
  which 
  appears 
  in 
  May. 
  In 
  both 
  species 
  

   the 
  larva 
  has 
  four 
  instars, 
  separated 
  by 
  ecdyses. 
  No 
  complete 
  account 
  of 
  these 
  larvae 
  

   appears 
  to 
  have 
  been 
  given 
  hitherto. 
  The 
  larva 
  and 
  pupa 
  of 
  D. 
  febrilis 
  have 
  been 
  

   figured 
  by 
  Curtis 
  (1844) 
  and 
  by 
  Cameron 
  (1913). 
  

  

  I 
  am 
  much 
  indebted 
  to 
  Dr. 
  A. 
  D. 
  Imms 
  for 
  suggestions 
  and 
  advice 
  during 
  the 
  

   course 
  of 
  this 
  work. 
  

  

  Dilophus 
  febrilis, 
  L. 
  

  

  Oviposition. 
  

  

  In 
  Dilophus 
  febrilis 
  the 
  circle 
  of 
  spines 
  at 
  the 
  distal 
  extremities 
  of 
  the 
  anterior 
  

   tibiae 
  appear 
  to 
  be 
  of 
  some 
  use 
  to 
  the 
  female 
  in 
  making 
  her 
  way 
  into 
  the 
  soil 
  for 
  the 
  

   purpose 
  of 
  oviposition. 
  The 
  fly 
  burrows 
  into 
  the 
  earth 
  by 
  pressing 
  the 
  soil 
  aside 
  

   by 
  this 
  means. 
  The 
  eggs 
  are 
  laid 
  in 
  a 
  mass 
  in 
  a 
  cell 
  in 
  the 
  soil 
  in 
  a 
  similar 
  manner 
  

   to 
  those 
  of 
  Bibio 
  marci, 
  as 
  figured 
  in 
  a 
  previous 
  paper 
  (Morris, 
  1921). 
  

  

  The 
  depth 
  of 
  the 
  soil 
  with 
  which 
  the 
  flies 
  were 
  supplied 
  was 
  only 
  2-5 
  cm., 
  but 
  

   several 
  masses 
  of 
  eggs 
  were 
  laid 
  at 
  that 
  depth, 
  against 
  the 
  bottom 
  of 
  the 
  vessel. 
  

  

  Egg- 
  

  

  The 
  eggs 
  of 
  Dilophus 
  febrilis 
  (fig. 
  1) 
  are 
  cylindrical 
  and 
  slightly 
  curved, 
  with 
  

   rounded 
  extremities, 
  the 
  diameter 
  at 
  one 
  end 
  being 
  slightly 
  greater 
  than 
  at 
  the 
  other. 
  

   When 
  first 
  laid 
  the 
  eggs 
  are 
  white, 
  but 
  they 
  soon 
  darken 
  at 
  both 
  extremities. 
  The 
  

   chorion 
  bears 
  numerous 
  slight 
  projections. 
  The 
  length 
  of 
  the 
  eggs 
  is 
  0-55 
  mm. 
  and 
  

   their 
  breadth 
  0-15 
  mm. 
  

  

  Fig. 
  1. 
  Eggs 
  of 
  Dilophus 
  febrilis, 
  L., 
  x 
  120. 
  

  

  Eggs 
  laid 
  on 
  19th 
  May 
  and 
  kept 
  in 
  the 
  laboratory, 
  hatched 
  on 
  7th 
  and 
  8th 
  June, 
  

   and 
  those 
  laid 
  on 
  21st 
  May 
  hatched 
  on 
  11th 
  June, 
  the 
  incubation 
  period 
  thus 
  being 
  

   18-20 
  days. 
  

  

  