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  58 
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  Leaves 
  of 
  plant 
  discolored, 
  and 
  lower 
  surface 
  covered 
  with 
  a 
  delicate, 
  

   loose, 
  and 
  dirty 
  webbing. 
  

  

  THE 
  RED 
  SPIDERS. 
  

  

  The 
  Common 
  Red 
  Spider. 
  

   Tetratiycluis 
  bimaculatus 
  Harv. 
  

  

  About 
  the 
  first 
  of 
  September, 
  1899, 
  during 
  a 
  period 
  of 
  uncommonly 
  

   dry 
  weather, 
  in 
  sugar-beet 
  fields 
  near 
  Tremont 
  and 
  Pekin, 
  III., 
  plants 
  

   were 
  observed 
  here 
  and 
  there, 
  most 
  commonly 
  near 
  the 
  margins 
  of 
  the 
  

   fields, 
  which 
  were 
  conspicuously 
  paler 
  than 
  the 
  rest, 
  many 
  of 
  the 
  leaves, 
  

   especially 
  the 
  larger 
  ones, 
  being 
  spotted 
  and 
  blotched 
  with 
  pale 
  yellow- 
  

   ish. 
  The 
  under 
  surface 
  of 
  the 
  leaf 
  beneath 
  these 
  faded 
  spots 
  was 
  un- 
  

   usually 
  dirty, 
  and 
  with 
  a 
  magnifier 
  was 
  seen 
  to 
  be 
  coated 
  with 
  a 
  fine 
  

   loose 
  web 
  containing 
  many 
  minute 
  particles; 
  and 
  moving 
  over 
  the 
  sur- 
  

   face 
  of 
  the 
  leaf 
  were 
  minute 
  oval 
  translucent 
  reddish 
  mites, 
  usually 
  

   marked 
  on 
  each 
  side 
  of 
  the 
  back 
  with 
  a 
  darker 
  blotch. 
  Many 
  of 
  the 
  

   dust-like 
  particles 
  in 
  the 
  web 
  on 
  these 
  leaves 
  were 
  evidently 
  empty 
  egg- 
  

   shells 
  of 
  the 
  mite, 
  and 
  others 
  were 
  its 
  globular 
  excreta. 
  Careful 
  com- 
  

   parison 
  of 
  these 
  specimens 
  and 
  of 
  those 
  found 
  abundant 
  on 
  hemp 
  in 
  the 
  

   vicinity 
  of 
  beet 
  fields 
  in 
  1900, 
  showed 
  that 
  all 
  belonged 
  to 
  the 
  species 
  

   mentioned 
  above. 
  

  

  The 
  injury 
  was 
  not 
  serious 
  here, 
  and 
  no 
  other 
  instance 
  of 
  the 
  occur- 
  

   rence 
  of 
  the 
  "red 
  spider" 
  in 
  beet 
  fields 
  came 
  to 
  our 
  knowledge 
  last 
  

   year; 
  but- 
  the 
  very 
  severe 
  injury 
  which 
  many 
  kinds 
  of 
  vegetation 
  suffer 
  

   from 
  these 
  mites, 
  particularly 
  in 
  hot 
  and 
  dry 
  weather, 
  makes 
  it 
  desirable 
  

   that 
  the 
  attention 
  of 
  beet 
  growers 
  should 
  be 
  called 
  to 
  them. 
  Although 
  

   they 
  are 
  commonly 
  more 
  injurious 
  to 
  greenhouse 
  plants 
  than 
  to 
  growths 
  

   in 
  the 
  open 
  air, 
  their 
  occurrence 
  on 
  trees, 
  shrubbery, 
  and 
  herbaceous 
  

   vegetation 
  generally 
  is 
  well 
  known. 
  ' 
  

  

  A 
  correct 
  idea 
  of 
  the 
  form 
  and 
  structure 
  of 
  this 
  mite 
  may 
  be 
  got 
  

   from 
  Fig. 
  i, 
  2, 
  3, 
  and 
  no 
  extended 
  description 
  need 
  be 
  given 
  here, 
  espe- 
  

   cially 
  as 
  other 
  species 
  of 
  the 
  genus 
  will 
  very 
  likely 
  be 
  found 
  abundant 
  

   on 
  the 
  beet 
  leaf. 
  The 
  life 
  history 
  of 
  these 
  mites 
  has 
  not 
  been 
  thoroughly 
  

   worked 
  out, 
  but 
  they 
  are 
  believed 
  to 
  winter 
  as 
  adults 
  among 
  dead 
  leaves, 
  

   in 
  the 
  crevices 
  of 
  sticks, 
  and 
  in 
  similar 
  shelters. 
  They 
  begin 
  to 
  breed 
  

   as 
  soon 
  as 
  the 
  weather 
  favors 
  their 
  multiplication 
  and 
  continue 
  active 
  

   throughout 
  the 
  season, 
  but 
  the 
  number 
  and 
  succession 
  of 
  generations 
  

   is 
  as 
  yet 
  unknown. 
  According 
  to 
  the 
  observations 
  of 
  Prof. 
  F. 
  L. 
  

   Harvey,* 
  by 
  whom 
  this 
  species 
  was 
  described, 
  it 
  infests 
  an 
  unusual 
  list 
  

   of 
  plants, 
  distributed 
  through 
  no 
  less 
  than 
  twenty-four 
  of 
  the 
  botanical 
  

   orders. 
  Those 
  worst 
  injured 
  at 
  Orono, 
  Me., 
  were 
  beans, 
  fuchsias, 
  

   wedding 
  bell 
  {Brugmansia^), 
  castor-oil 
  plant, 
  and 
  Boston 
  smilax 
  {Myr- 
  

  

  *Ann. 
  Rep. 
  Me. 
  Agr. 
  Exper. 
  Station, 
  1892, 
  p. 
  133. 
  

  

  