﻿HABITS 
  OF 
  THE 
  ADULT. 
  21 
  

  

  and 
  earlier 
  leaves 
  are 
  first 
  attacked 
  in 
  the 
  spring 
  by 
  the 
  adults. 
  

   These 
  feed 
  on 
  the 
  underside 
  of 
  the 
  leaves, 
  scraping 
  out 
  the 
  leaf 
  

   content 
  in 
  small 
  spots 
  that 
  become 
  white 
  and 
  conspicuous. 
  Often 
  

   the 
  adults 
  move 
  along 
  and 
  leave 
  a 
  chain 
  of 
  white 
  spots 
  to 
  mark 
  their 
  

   progress. 
  The 
  adults 
  also 
  feed 
  to 
  some 
  extent 
  on 
  the 
  surface. 
  

   As 
  they 
  feed 
  the 
  females 
  deposit 
  their 
  eggs 
  in 
  the 
  leaf 
  tissues, 
  and 
  

   as 
  soon 
  as 
  incubation 
  is 
  completed 
  the 
  larvae 
  hatch 
  and 
  join 
  the 
  

   adults 
  on 
  the 
  leaves. 
  Under 
  these 
  conditions 
  the 
  leaves 
  become 
  more 
  

   or 
  less 
  dried 
  and 
  lifeless, 
  and 
  the 
  adults 
  move 
  to 
  the 
  higher 
  and 
  more 
  

   tender 
  leaves 
  of 
  the 
  plant. 
  In 
  this 
  way 
  the 
  entire 
  plant 
  may 
  become 
  

   infested. 
  On 
  February 
  5, 
  1911, 
  the 
  writer 
  found 
  the 
  adults 
  of 
  this 
  

   insect 
  extremely 
  abundant 
  in 
  the 
  pea 
  field 
  of 
  some 
  Chinese 
  truckers 
  

   at 
  Hollywood, 
  Cal. 
  Here 
  nearly 
  every 
  plant 
  had 
  7 
  or 
  8 
  adults 
  feed- 
  

   ing 
  on 
  the 
  underside 
  of 
  the 
  foliage, 
  and 
  in 
  many 
  cases 
  5 
  and 
  6 
  were 
  

   present 
  on 
  each 
  leaf. 
  On 
  August 
  18 
  of 
  the 
  same 
  year 
  in 
  the 
  same 
  

   locality 
  plants 
  of 
  spiny 
  wild 
  lettuce 
  (Lactuca 
  scariola) 
  were 
  observed 
  

   that 
  had 
  50 
  adults 
  feeding 
  on 
  a 
  single 
  leaf. 
  

  

  The 
  adults 
  seem 
  to 
  feed 
  on 
  a 
  large 
  variety 
  of 
  plants 
  and 
  have 
  been 
  

   found 
  feeding 
  on 
  all 
  of 
  the 
  plants 
  given 
  under 
  " 
  List 
  of 
  food 
  plants." 
  

   It 
  may 
  be 
  well 
  to 
  state 
  at 
  this 
  point 
  that 
  the 
  presence 
  of 
  adults 
  on 
  a 
  

   plant 
  has 
  not 
  been 
  considered 
  sufficient 
  evidence 
  to 
  class 
  that 
  plant 
  

   as 
  a 
  food 
  plant, 
  but 
  whenever 
  larvae 
  of 
  this 
  insect 
  were 
  taken 
  on 
  a 
  

   plant, 
  this 
  was 
  considered 
  sufficient 
  to 
  rank 
  the 
  plant 
  as 
  a 
  host. 
  

  

  In 
  the 
  spring 
  when 
  the 
  adults 
  leave 
  hibernation 
  they 
  collect 
  on 
  

   the 
  wild 
  food 
  plants 
  present 
  and 
  feed 
  on 
  them 
  until 
  their 
  injury, 
  

   due 
  to 
  an 
  increase 
  in 
  numbers 
  and 
  feeding, 
  weakens 
  the 
  plants 
  and 
  

   shortens 
  the 
  food 
  supply; 
  then 
  they 
  fly 
  to 
  fresh 
  plants 
  of 
  the 
  same 
  

   hosts 
  or 
  to 
  cultivated 
  crops 
  and 
  fruit 
  trees 
  nearby. 
  Of 
  all 
  the 
  food 
  

   plants 
  observed, 
  the 
  spiny 
  wild 
  lettuce 
  {Lactuca 
  scariola) 
  seems 
  to 
  

   be 
  the 
  most 
  favored. 
  This 
  plant 
  has 
  been 
  found 
  to 
  be 
  infested 
  more 
  

   heavily 
  than 
  any 
  of 
  the 
  other 
  food 
  plants 
  concerned, 
  not 
  excepting 
  

   those 
  of 
  economic 
  importance. 
  

  

  FLIGHT. 
  

  

  The 
  present 
  writer 
  in 
  his 
  investigations 
  of 
  the 
  greenhouse 
  thrips 
  l 
  

   never 
  observed 
  that 
  insect 
  to 
  take 
  flight 
  naturally, 
  or 
  even 
  when 
  dis- 
  

   turbed. 
  The 
  adults 
  of 
  Ileliothrips 
  fasciatus, 
  on 
  the 
  contrary, 
  take 
  

   flight 
  very 
  readily, 
  and 
  if 
  jarred 
  or 
  disturbed 
  will 
  usually 
  fly 
  or 
  jump. 
  

   This 
  species 
  in 
  taking 
  flight 
  raises 
  the 
  tip 
  of 
  the 
  abdomen 
  quick 
  I 
  v. 
  

   and 
  separates 
  the 
  wings. 
  It 
  then 
  rises 
  straight 
  up 
  into 
  the 
  air 
  and 
  

   flies 
  rapidly 
  away 
  in 
  short 
  undulating 
  curves. 
  Indeed, 
  to 
  the 
  un- 
  

   trained 
  eye 
  it 
  appears, 
  in 
  flight, 
  exactly 
  like 
  a 
  small 
  speck 
  of 
  soot 
  

   being 
  blown 
  around 
  by 
  a 
  -light 
  breeze. 
  This 
  power 
  of 
  flight 
  aids 
  

   greatly 
  in 
  the 
  dispersion 
  of 
  this 
  insect 
  during 
  the 
  spring 
  and 
  summer. 
  

  

  1 
  Loc. 
  cit. 
  

  

  