﻿32 
  

  

  THE 
  BEAN 
  THKIPS. 
  

  

  leaves 
  of 
  wild 
  lettuce 
  were 
  collected 
  on 
  April 
  7 
  and 
  they 
  had 
  a 
  

   number 
  of 
  eggs 
  in 
  them 
  very 
  recently 
  laid. 
  The 
  last 
  of 
  these 
  hatched 
  

   on 
  April 
  24, 
  making 
  the 
  length 
  of 
  incubation 
  about 
  17 
  days, 
  or 
  possi- 
  

   bly 
  as 
  many 
  as 
  21 
  days. 
  The 
  average 
  mean 
  temperature 
  for 
  these 
  

   21 
  days 
  was 
  59.1° 
  F. 
  

  

  In 
  July 
  several 
  adults 
  of 
  this 
  thrips 
  were 
  confined 
  over 
  night 
  on 
  

   leaves 
  of 
  growing 
  plants 
  that 
  were 
  uninfested, 
  and 
  were 
  removed 
  

   on 
  the 
  following 
  morning. 
  In 
  this 
  way 
  a 
  number 
  of 
  eggs 
  were 
  ob- 
  

   tained 
  that 
  hatched 
  under 
  absolutely 
  normal 
  conditions, 
  as 
  the 
  plants 
  

   were 
  kept 
  in 
  an 
  open-air 
  insectary. 
  

  

  Table 
  IV 
  has 
  been 
  prepared 
  to 
  show 
  the 
  records 
  of 
  incubation 
  for 
  

   these 
  eggs. 
  

  

  Table 
  IV. 
  — 
  Length 
  of 
  egg 
  stage 
  of 
  the 
  bean 
  thrips 
  in 
  July 
  at 
  Compton, 
  Cal., 
  1911. 
  

  

  Date 
  of 
  

   ovipo- 
  

   sition. 
  

  

  Dates 
  eggs 
  hatched 
  and 
  number 
  each 
  day. 
  

  

  Julv 
  

   23/ 
  

  

  Julv 
  

   24 
  

  

  Julv 
  

   25/ 
  

  

  July 
  

   26. 
  

  

  July 
  

   27. 
  

  

  July 
  July 
  July 
  

   29. 
  30. 
  

  

  First 
  egg 
  

   hatched. 
  

  

  Last 
  egg 
  

   hatched. 
  

  

  Shortest 
  

   incuba- 
  

   tion. 
  

  

  Longest 
  

   incuba- 
  

   tion. 
  

  

  Total 
  

  

  eggs 
  

  

  hatched. 
  

  

  July 
  10 
  

   July 
  11 
  

   July 
  14 
  

  

  15 
  

  

  July 
  23 
  

   July 
  24 
  

   July 
  28 
  

  

  Julv 
  28 
  

   July 
  27 
  

   July 
  29 
  

  

  Days. 
  

  

  Days. 
  

  

  23 
  

  

  In 
  this 
  experiment 
  169 
  eggs 
  hatched 
  and 
  the 
  minimum 
  length 
  of 
  

   incubation 
  Avas 
  13 
  days 
  and 
  the 
  maximum 
  18 
  days, 
  but 
  nearly 
  50 
  

   per 
  cent 
  hatched 
  in 
  just 
  14 
  days. 
  During 
  this 
  total 
  period 
  the 
  aver- 
  

   age 
  mean 
  temperature 
  was 
  69.6° 
  F. 
  

  

  Again, 
  on 
  August 
  20 
  adults 
  were 
  confined 
  over 
  night 
  on 
  a 
  living 
  

   plant 
  of 
  wild 
  lettuce, 
  and 
  4 
  larvae 
  hatched 
  on 
  September 
  4, 
  and 
  7 
  on 
  

   September 
  5, 
  making 
  the 
  periods 
  of 
  incubation 
  15 
  and 
  16 
  days. 
  

   During 
  this 
  time 
  the 
  average 
  mean 
  temperature 
  was 
  66.3° 
  F. 
  

  

  During 
  the 
  months 
  of 
  October 
  and 
  November 
  the 
  incubation 
  is 
  

   probably 
  lengthened 
  a 
  few 
  days 
  and 
  will 
  take 
  about 
  21 
  days, 
  as 
  the 
  

   average 
  mean 
  temperature 
  for 
  these 
  months 
  was, 
  respectively, 
  58,67° 
  

   and 
  55.3° 
  F. 
  

  

  THE 
  LARVA. 
  

  

  The 
  length 
  of 
  time 
  occupied 
  by 
  this 
  insect 
  in 
  the 
  larval 
  stage 
  dur- 
  

   ing 
  the 
  months 
  of 
  March, 
  April, 
  and 
  May 
  was 
  observed 
  during 
  the 
  

   year 
  1911 
  by 
  confining 
  larva? 
  that 
  had 
  just 
  emerged 
  in 
  vials 
  con- 
  

   stantly 
  supplied 
  with 
  fresh 
  food. 
  Table 
  V 
  gives 
  the 
  results 
  of 
  these 
  

   observations. 
  While 
  in 
  the 
  first 
  part 
  of 
  this 
  period 
  the 
  length 
  re- 
  

   quired 
  was 
  from 
  17 
  to 
  19 
  days, 
  later 
  it 
  was 
  shortened 
  to 
  9 
  and 
  11 
  

   days. 
  The 
  average 
  mean 
  temperature 
  for 
  the 
  first 
  period, 
  March 
  

   19 
  to 
  April 
  7, 
  was 
  61.5° 
  F. 
  and 
  for 
  May 
  14 
  to 
  May 
  27 
  it 
  was 
  61.1° 
  F. 
  

  

  