﻿ORCHARD 
  INSECTS 
  PACIFIC 
  NORTHWEST 
  

  

  25 
  

  

  vouring 
  all 
  the 
  leaf 
  tissue 
  except 
  

   the 
  midribs, 
  and 
  retire 
  at 
  night 
  to 
  

   the 
  tents, 
  or 
  collect 
  in 
  masses 
  on 
  

   the 
  larger 
  limbs. 
  These 
  caterpil- 
  

   lars 
  occur 
  sporadically 
  and 
  in 
  

   some 
  years 
  are 
  numerous 
  enough 
  

   to 
  defoliate 
  not 
  only 
  fruit 
  trees 
  but 
  

   wild 
  growth 
  and 
  shade 
  trees 
  as 
  

   well. 
  

  

  Figure 
  31. 
  — 
  Nest 
  of 
  the 
  eastern 
  tent 
  

   caterpillar. 
  

  

  LIFE 
  HISTORY 
  

  

  The 
  insect 
  winters 
  in 
  the 
  egg 
  

   stage. 
  The 
  eggs 
  are 
  laid 
  in 
  masses 
  

   surrounding 
  the 
  twigs, 
  each 
  mass 
  

   containing 
  several 
  hundred 
  eggs 
  

   covered 
  with 
  a 
  frothy, 
  waterproof 
  

   material. 
  The 
  young 
  caterpillars 
  

   appear 
  about 
  the 
  time 
  the 
  apple 
  

   buds 
  begin 
  to 
  open. 
  The 
  group 
  

   hatching 
  from 
  a 
  single 
  egg 
  mass 
  

   constructs 
  a 
  small 
  silken 
  nest 
  or 
  

   tent, 
  and 
  as 
  the 
  caterpillars 
  grow 
  

   this 
  nest 
  is 
  enlarged 
  to 
  provide 
  

   adequate 
  protection 
  for 
  the 
  colony. 
  

   The 
  caterpillars 
  are 
  somewhat 
  

   hairy, 
  tawny 
  brown, 
  Avith 
  a 
  row 
  

   of 
  blue 
  spots 
  flanked 
  by 
  orange 
  

   spots 
  along 
  the 
  back. 
  When 
  full- 
  

  

  890478°— 
  50 
  4 
  

  

  grown 
  they 
  are 
  nearly 
  2 
  inches 
  

   long. 
  As 
  the 
  caterpillars 
  become 
  

   larg-er 
  they 
  tend 
  to 
  scatter, 
  and 
  

   their 
  cocoons 
  may 
  be 
  spun 
  in 
  vari- 
  

   ous 
  sheltered 
  places, 
  such 
  as 
  under 
  

   loose 
  bark, 
  in 
  curled 
  leaves, 
  or 
  

   under 
  projecting 
  eaves 
  of 
  nearby 
  

   buildings. 
  The 
  cocoons 
  are 
  tight- 
  

   ly 
  woven 
  of 
  yellow 
  silk, 
  sur- 
  

   rounded 
  with 
  a 
  loose 
  mass 
  of 
  silk. 
  

   The 
  moths 
  emerge 
  in 
  June 
  or 
  July 
  

   and 
  soon 
  deposit 
  the 
  overwinter- 
  

   ing 
  egg 
  masses. 
  

  

  CONTROL 
  

  

  Many 
  of 
  the 
  egg 
  masses 
  may 
  be 
  

   found 
  and 
  destroyed 
  when 
  the 
  

   trees 
  are 
  pruned. 
  If 
  the 
  small 
  

   caterpillars 
  are 
  numerous, 
  a 
  spray 
  

   containing 
  lead 
  arsenate 
  or 
  50-per- 
  

   cent 
  DDT 
  wettable 
  powder, 
  2 
  

   pounds 
  to 
  100 
  gallons, 
  applied 
  just 
  

   before 
  the 
  trees 
  bloom 
  is 
  very 
  ef- 
  

   fective. 
  If 
  the 
  spraying 
  is 
  done 
  

   later, 
  the 
  quantity 
  of 
  lead 
  arsenate 
  

   should 
  be 
  doubled, 
  as 
  the 
  larger 
  

   caterpillars 
  are 
  more 
  resistant 
  to 
  

   the 
  poison. 
  Often 
  the 
  tents 
  can 
  be 
  

   pruned 
  out 
  and 
  destroyed, 
  or 
  

   burned 
  out 
  with 
  a 
  torch; 
  care 
  

   should 
  be 
  taken 
  to 
  move 
  the 
  flame 
  

   rapidly 
  so 
  as 
  not 
  to 
  injure 
  the" 
  tree. 
  

   The 
  tents 
  should 
  be 
  destroyed 
  at 
  

   night 
  when 
  most 
  of 
  the 
  caterpil- 
  

   lars 
  are 
  congregated 
  in 
  them. 
  

  

  Fall 
  Webworm 
  

  

  Although 
  the 
  habits 
  of 
  the 
  fall 
  

   webworm 
  are 
  somewhat 
  similar 
  to 
  

   those 
  of 
  the 
  tent 
  caterpillar, 
  the 
  

   two 
  insects 
  can 
  be 
  easily 
  distin- 
  

   guished. 
  As 
  the 
  name 
  implies, 
  the 
  

   fall 
  webworm 
  appears 
  late 
  in 
  the 
  

   summer 
  and 
  constructs 
  a 
  loose 
  and 
  

   unsightly 
  nest 
  of 
  webbing 
  about 
  a 
  

   number 
  of 
  twigs 
  (fig. 
  32). 
  These 
  

   nests 
  are 
  extended 
  as 
  the 
  cater- 
  

   pillars 
  grow 
  and 
  often 
  enclose 
  en- 
  

   tire 
  branches. 
  The 
  caterpillars 
  

   feed 
  within 
  the 
  webs, 
  devouring 
  

   the 
  leaves 
  and 
  fruit. 
  When 
  full- 
  

   grown 
  the 
  caterpillar 
  is 
  about 
  1% 
  

   inches 
  long, 
  covered 
  with 
  long, 
  

  

  