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  MYCETOPHILID 
  FLIES 
  AS 
  PESTS 
  OF 
  THE 
  CUCUMBER 
  PLANT 
  IN 
  

  

  GLASS-HOUSES. 
  

  

  By 
  E. 
  R. 
  Speyer, 
  M.A., 
  F.E.S., 
  

  

  Entomologist, 
  Experimental 
  and 
  Research 
  Station, 
  Cheshunt, 
  Herts. 
  

  

  (Plate 
  X.) 
  

  

  Severe 
  injury 
  to 
  the 
  roots 
  of 
  cucumber 
  plants 
  has 
  occurred 
  since 
  January 
  of 
  this 
  

   year 
  (1922) 
  through 
  the 
  attacks 
  of 
  the 
  larvae 
  of 
  certain 
  minute 
  " 
  fungus-gnats 
  " 
  

   belonging 
  to 
  the 
  family 
  Sciaridae. 
  Although 
  such 
  attacks 
  have 
  not 
  been 
  recorded 
  

   previously 
  by 
  growers 
  of 
  cucumbers, 
  it 
  is 
  more 
  than 
  probable 
  that 
  the 
  flies 
  have 
  been 
  

   present 
  in 
  glass-houses 
  for 
  a 
  number 
  of 
  years, 
  and 
  that 
  damage 
  arising 
  through 
  their 
  

   agency 
  has 
  mistakenly 
  been 
  attributed 
  to 
  " 
  eel-worms." 
  

  

  The 
  first 
  serious 
  outbreak 
  was 
  recorded 
  in 
  January, 
  a 
  very 
  large 
  number 
  of 
  pot- 
  

   plants 
  having 
  been 
  damaged 
  to 
  the 
  point 
  of 
  destruction 
  in 
  a 
  nursery 
  at 
  Enfield 
  Wash. 
  

   The 
  matter 
  was 
  taken 
  up, 
  and 
  the 
  causative 
  factor 
  proved 
  beyond 
  doubt 
  to 
  be 
  larvae 
  

   of 
  Pnyxia 
  {Epidapus) 
  scabiei, 
  Hopk. 
  A 
  description 
  of 
  P. 
  scabiei 
  has 
  been 
  given 
  by 
  

   Dr. 
  A. 
  D. 
  Hopkins 
  in 
  the 
  Proceedings 
  of 
  the 
  Entomological 
  Society 
  of 
  Washington, 
  

   vol. 
  iii, 
  p. 
  152, 
  in 
  1895, 
  when 
  the 
  larvae 
  of 
  this 
  fly 
  were 
  regarded 
  as 
  at 
  any 
  rate 
  one 
  of 
  

   the 
  causes 
  of 
  the 
  disease 
  known 
  as 
  " 
  potato 
  scab." 
  

  

  Fig. 
  1. 
  Pnyxia 
  scabiei, 
  Hopk., 
  eggs, 
  X 
  60. 
  

  

  Fig. 
  2. 
  Larva 
  of 
  Pnyxia 
  scabiei, 
  Hopk., 
  x 
  33. 
  

  

  As 
  the 
  publication 
  referred 
  to 
  is 
  not 
  readily 
  available, 
  a 
  few 
  of 
  the 
  more 
  important 
  

   points 
  in 
  the 
  life-history 
  are 
  here 
  taken 
  from 
  Dr. 
  Hopkins's 
  paper. 
  The 
  eggs 
  (fig. 
  1) 
  

   are 
  laid 
  by 
  the 
  female 
  fly 
  to 
  the 
  number 
  of 
  20-30 
  in 
  soil 
  or 
  manure, 
  and 
  take 
  5-6 
  days 
  

   in 
  hatching. 
  The 
  larvae 
  (fig. 
  2), 
  which 
  are 
  white 
  with 
  black 
  heads, 
  feed 
  for 
  a 
  period 
  

  

  (8053) 
  s 
  

  

  