﻿256 
  

  

  E. 
  R. 
  SPEYER. 
  

  

  of 
  7-8 
  days. 
  Finally 
  they 
  spin 
  a 
  cocoon 
  of 
  a 
  dark 
  silky 
  substance, 
  in 
  which 
  they 
  

   turn 
  to 
  a 
  white 
  pupa 
  (fig. 
  3), 
  the 
  adult 
  fly 
  emerging 
  three 
  days 
  later. 
  The 
  female 
  fly 
  

   is 
  wingless 
  (fig. 
  4), 
  and 
  the 
  males 
  are 
  of 
  two 
  kinds, 
  one 
  with 
  long 
  and 
  the 
  other 
  with 
  

   short 
  wings 
  (figs. 
  5, 
  6). 
  The 
  female 
  deposits 
  the 
  eggs 
  5-6 
  days 
  after 
  emergence. 
  

   Broods 
  of 
  flies 
  appear 
  every 
  20-25 
  days. 
  

  

  Fig. 
  3. 
  Pupa 
  of 
  Pnyxia 
  scabiei, 
  Hopk., 
  X 
  33. 
  

  

  Fig. 
  4. 
  Pnyxia 
  scabiei, 
  Hopk., 
  $, 
  X 
  33. 
  

  

  Fig. 
  5. 
  Pnyxia 
  scabiei, 
  Hopk., 
  (J, 
  long-winged 
  form, 
  x 
  33. 
  

  

  Details 
  relating 
  to 
  the 
  attack 
  of 
  Pnyxia 
  scabiei 
  on 
  cucumbers 
  at 
  Enfield 
  Wash 
  

   are 
  now 
  given. 
  

  

  The 
  cucumber 
  plants 
  were 
  potted 
  out 
  from 
  the 
  seed-boxes 
  (in 
  which 
  there 
  had 
  

   been 
  no 
  attack) 
  in 
  the 
  middle 
  of 
  December 
  1921 
  ; 
  the 
  pot-soil 
  was 
  unsterilised 
  and 
  

   mixed 
  with 
  horse 
  manure. 
  Attack 
  by 
  the 
  grubs 
  was 
  first 
  noted 
  on 
  8th 
  January 
  1922, 
  

   and 
  between 
  then 
  and 
  12th 
  January 
  some 
  600 
  plants 
  were 
  destroyed. 
  The 
  tap-root 
  

   of 
  the 
  infected 
  plants 
  had 
  been 
  eaten 
  into 
  by 
  the 
  larvae, 
  and 
  hollowed 
  out 
  from 
  below 
  

   upwards 
  to 
  within 
  quarter-inch 
  to 
  half-inch 
  below 
  the 
  soil 
  surface. 
  Some 
  root 
  stems 
  

   contained 
  as 
  many 
  as 
  60 
  larvae. 
  On 
  no 
  part 
  of 
  the 
  plant 
  were 
  any 
  eggs 
  found. 
  When 
  

   full-fed 
  the 
  larvae 
  ate 
  their 
  way 
  out 
  of 
  the 
  stem 
  below 
  the 
  ground 
  and 
  pupated 
  in. 
  

  

  