﻿26 
  THE 
  BEAN 
  THKIPS. 
  

  

  The 
  molting 
  from 
  larva 
  to 
  prepupa 
  under 
  laboratory 
  conditions 
  has 
  

   been 
  observed 
  many 
  times. 
  On 
  April 
  10, 
  1911, 
  a 
  mature 
  larva 
  was 
  

   observed 
  to 
  begin 
  the 
  process 
  at 
  4.05 
  in 
  the 
  afternoon. 
  After 
  remain- 
  

   ing 
  motionless 
  for 
  some 
  time 
  it 
  arched 
  its 
  body, 
  and 
  shortly 
  after 
  

   the 
  skin 
  split 
  down 
  the 
  head 
  behind 
  the 
  antennae. 
  The 
  head 
  grad- 
  

   ually 
  forced 
  its 
  way 
  out 
  of 
  the 
  opening, 
  then 
  the 
  body 
  followed,' 
  the 
  

   old 
  skin 
  being 
  slipped 
  off 
  behind. 
  This 
  molting 
  was 
  completed 
  at 
  

   4.21 
  p. 
  m. 
  

  

  HABITS 
  OF 
  THE 
  PREPUPA 
  AND 
  PUPA. 
  

  

  The 
  prepupae 
  of 
  this 
  insect 
  are 
  found 
  in 
  company 
  with 
  the 
  pupae 
  

   and 
  full-grown 
  larvae 
  in 
  small 
  social 
  colonies. 
  These 
  hold 
  the 
  

   antennae 
  out 
  in 
  front 
  of 
  the 
  body 
  and 
  move 
  about 
  to 
  some 
  extent. 
  

   The 
  pupae, 
  however, 
  carry 
  the 
  antennae 
  folded 
  back 
  on 
  the 
  head 
  and 
  

   thorax 
  and 
  remain 
  motionless 
  unless 
  disturbed 
  or 
  exposed 
  to 
  the 
  

   light, 
  in 
  which 
  cases 
  they 
  will 
  slowly 
  crawl 
  away. 
  When 
  com- 
  

   pelled 
  to 
  pupate 
  in 
  closed 
  vials 
  the 
  prepupae 
  and 
  pupae 
  occur 
  in 
  

   large 
  numbers 
  closely 
  packed 
  together 
  along 
  the 
  edge 
  of 
  the 
  vial 
  

   and 
  the 
  cotton 
  plug 
  or 
  buried 
  in 
  the 
  cotton 
  itself. 
  In 
  nature 
  it 
  has 
  

   quite 
  different 
  habits. 
  While 
  the 
  greenhouse 
  thrips 
  under 
  natural 
  

   conditions 
  pupates 
  on 
  the 
  leaf 
  of 
  the 
  food 
  plant 
  in 
  among 
  the 
  feeding 
  

   larvae, 
  with 
  the 
  bean 
  thrips 
  this 
  seldom 
  takes 
  place, 
  and 
  during 
  the 
  

   two 
  years 
  this 
  species 
  has 
  been 
  under 
  observation 
  by 
  the 
  writer 
  only 
  

   three 
  pupae 
  have 
  been 
  found 
  on 
  the 
  plants 
  infested 
  by 
  hundreds 
  of 
  

   thousands 
  of 
  larvae. 
  In 
  one 
  case 
  a 
  pupa 
  was 
  found 
  under 
  the 
  web 
  of 
  

   the 
  red 
  spider 
  near 
  the 
  midrib 
  of 
  a 
  leaf 
  of 
  spiny 
  lettuce 
  ; 
  in 
  another, 
  

   one 
  was 
  found 
  under 
  a 
  web 
  of 
  red 
  spider 
  on 
  a 
  leaf 
  of 
  the 
  wild 
  tobacco 
  

   flower; 
  and 
  the 
  third 
  was 
  found 
  in 
  a 
  curled-up 
  lettuce 
  leaf. 
  

  

  December 
  17, 
  1910, 
  a 
  quantity 
  of 
  the 
  dead 
  leaves 
  of 
  wild 
  helio- 
  

   trope 
  were 
  collected 
  on 
  the 
  ground 
  under 
  infested 
  plants. 
  Prolonged 
  

   sifting 
  revealed 
  the 
  presence 
  of 
  a 
  single 
  pupa. 
  In 
  1911, 
  the 
  prepupae 
  

   and 
  pupae 
  were 
  found 
  by 
  Mr. 
  John 
  E. 
  Graf 
  and 
  the 
  writer 
  to 
  be 
  

   very 
  abundant 
  in 
  infested 
  bean 
  fields 
  under 
  clods 
  or 
  lumps 
  of 
  dry 
  

   earth 
  and 
  in 
  cracks 
  or 
  holes 
  in 
  the 
  lumps. 
  Upon 
  exposure 
  to 
  the 
  

   light 
  these 
  at 
  once 
  began 
  to 
  move 
  away 
  in 
  search 
  of 
  darkness. 
  

  

  Mr. 
  Wildermuth 
  also 
  found 
  the 
  pupae 
  of 
  this 
  insect 
  underground. 
  

   He 
  wrote 
  in 
  his 
  notes 
  on 
  September 
  23 
  : 
  

  

  While 
  searching 
  by 
  aid 
  of 
  a 
  binocular 
  for 
  pupae, 
  I 
  found 
  one 
  pupa, 
  one 
  

   prepupa, 
  and 
  two 
  (mature) 
  larvse 
  just 
  at 
  the 
  crown 
  of 
  the 
  plant 
  and 
  beneath 
  

   the 
  soil 
  ; 
  one 
  pupa 
  about 
  one-fourth 
  inch 
  below 
  the 
  surface 
  of 
  the 
  soil 
  in 
  an 
  

   oval 
  cavity 
  about 
  three 
  times 
  as 
  long 
  as 
  the 
  pupa 
  itself; 
  one 
  prepupa 
  between 
  a 
  

   dead 
  leaf 
  and 
  the 
  soil. 
  Never 
  have 
  I 
  found 
  a 
  pupa 
  above 
  the 
  surface 
  of 
  the 
  

   ground, 
  on 
  the 
  leaves 
  of 
  the 
  plant, 
  or 
  between 
  the 
  sheath 
  leaves 
  and 
  the 
  stem, 
  

   as 
  frequently 
  occurs 
  in 
  confinement. 
  

  

  The 
  molding 
  of 
  the 
  prepupa 
  to 
  the 
  pupal 
  stage 
  is 
  very 
  similar 
  to 
  

   that 
  descried 
  for 
  the 
  change 
  of 
  the 
  larva 
  to 
  the 
  prepupa. 
  It 
  takes 
  

  

  