﻿NATUKAL 
  CONTROL. 
  41 
  

  

  that 
  crotons, 
  which 
  in 
  the 
  greenhouse 
  were 
  infested 
  with 
  thousands 
  

   of 
  thrips 
  and 
  which 
  in 
  June 
  were 
  placed 
  outside 
  and 
  subjected 
  to 
  

   the 
  Florida 
  summer 
  rains, 
  when 
  examined 
  in 
  September 
  were 
  so 
  free 
  

   from 
  this 
  insect 
  that 
  it 
  was 
  almost 
  impossible 
  to 
  find 
  specimens. 
  

  

  California, 
  with 
  its 
  long 
  dry 
  season, 
  does 
  not 
  obtain 
  the 
  same 
  

   benefit, 
  but 
  even 
  there 
  the 
  rains 
  may 
  reduce 
  attacks 
  of 
  the 
  bean 
  thrips 
  

   to 
  some 
  extent. 
  On 
  February 
  7, 
  1911, 
  the 
  writer 
  observed 
  a 
  pea 
  

   field 
  that 
  had 
  from 
  5 
  to 
  8 
  adults 
  on 
  every 
  plant. 
  After 
  this 
  date 
  

   there 
  was 
  a 
  severe 
  rain 
  of 
  several 
  days' 
  duration, 
  and 
  when 
  the 
  

   field 
  was 
  again 
  examined, 
  on 
  April 
  1, 
  it 
  was 
  almost 
  impossible 
  to 
  

   find 
  the 
  thrips. 
  Mr. 
  Graf, 
  writing 
  from 
  Puente, 
  Cal., 
  on 
  October 
  6, 
  

   1911, 
  noted 
  that 
  the 
  larvae 
  were 
  much 
  scarcer 
  than 
  a 
  week 
  earlier, 
  

   probably 
  owing 
  to 
  a 
  rainfall 
  of 
  one-half 
  inch. 
  Mr. 
  Wildermuth, 
  

   at 
  Tempe, 
  Ariz., 
  wrote 
  on 
  October 
  5, 
  1911 
  : 
  

  

  A 
  search 
  in 
  the 
  patch 
  of 
  alfalfa 
  back 
  of 
  the 
  office, 
  where 
  thrips 
  had 
  been 
  

   very 
  numerous 
  for 
  several 
  weeks, 
  failed 
  to 
  reveal 
  very 
  many 
  thrips 
  to-day. 
  

   The 
  heavy 
  rain 
  of 
  yesterday 
  and 
  last 
  night 
  was 
  probably 
  responsible 
  for 
  

   washing 
  them 
  off. 
  

  

  In 
  California, 
  then, 
  late 
  rains 
  in 
  the 
  spring 
  may 
  greatly 
  diminish 
  

   the 
  numbers 
  of 
  this 
  insect, 
  or 
  early 
  rains 
  in 
  the 
  fall 
  destroy 
  many 
  

   that 
  otherwise 
  would 
  enter 
  hi- 
  

  

  natural 
  en 
  e.mies. 
  -^^m!§umml^^ 
  ^^XkmjmJmmiB^ 
  

  

  Fig. 
  10. 
  — 
  The 
  bean 
  thrips: 
  Prepupse 
  parasit- 
  

   A 
  great 
  deal 
  of 
  attention 
  has 
  ized 
  ^ 
  Thripoctenus 
  ruaselli. 
  Much 
  en- 
  

  

  ° 
  . 
  „ 
  larged. 
  (Author's 
  illustration.) 
  

  

  been 
  given 
  to 
  the 
  subject 
  ol 
  

  

  natural 
  enemies 
  and 
  some 
  information 
  obtained 
  on 
  this 
  important 
  

  

  feature 
  of 
  insect 
  control. 
  

  

  In 
  the 
  fall 
  of 
  1910 
  the 
  larva 
  of 
  this 
  thrips 
  was 
  discovered 
  to 
  be 
  

   parasitized 
  (see 
  fig. 
  10) 
  by 
  a 
  minute 
  hymenopteron. 
  This 
  was 
  de- 
  

   scribed 
  by 
  Mr. 
  J. 
  C. 
  Crawford 
  as 
  Thripoctenus 
  russelli 
  (see 
  fig. 
  11). 
  

   During 
  1911 
  this 
  parasite 
  was 
  observed 
  to 
  work 
  extensively 
  in 
  Los 
  

   Angeles 
  County 
  on 
  the 
  bean 
  thrips 
  and 
  seemed 
  to 
  destroy 
  large 
  

   numbers. 
  Some 
  collections 
  of 
  thrips 
  larva? 
  gave 
  as 
  high 
  as 
  70 
  per 
  

   cent 
  killed 
  by 
  the 
  parasite. 
  For 
  a 
  full 
  account 
  of 
  this 
  parasite 
  the 
  

   reader 
  is 
  referred 
  to 
  Technical 
  Series 
  23, 
  Part 
  II, 
  Bureau 
  of 
  Ento- 
  

   mology, 
  United 
  States 
  Department 
  of 
  Agriculture. 
  

  

  During 
  1911 
  the 
  larva 
  of 
  a 
  green 
  lacewing 
  fly 
  (Chrysopa 
  cali- 
  

   fomica 
  Coq.) 
  was 
  commonly 
  observed 
  feeding 
  on 
  the 
  larva 
  of 
  this 
  

   thrips. 
  As 
  this 
  insect 
  was 
  observed 
  so 
  engaged 
  in 
  several 
  localities 
  

   in 
  Los 
  Angeles 
  County, 
  and 
  in 
  noticeable 
  numbers, 
  it 
  probably 
  kills 
  

   a 
  large 
  number 
  of 
  thrips. 
  

  

  The 
  larva 
  of 
  a 
  syrphid 
  fly 
  (SphoBrophoria 
  sulphuripes 
  Thomson) 
  

   was 
  also 
  observed 
  on 
  numerous 
  occasion-- 
  feeding 
  <>n 
  the 
  larva 
  of 
  

  

  