﻿— 
  ii6 
  — 
  

  

  The 
  Yellow-Back 
  Flea-beetle. 
  

  

  Disonycha 
  xantJiomehcna 
  Dalm. 
  

  

  ^Disonycha 
  collar 
  is 
  Fabr.) 
  

  

  (PI. 
  v., 
  VI.) 
  

  

  At 
  any 
  time 
  throughout 
  the 
  season 
  from 
  early 
  spring 
  to 
  fall 
  the 
  

   beet 
  leaves 
  may 
  become 
  riddled 
  with 
  small 
  round 
  holes 
  usually 
  from 
  an 
  

   eighth 
  to 
  a 
  fourth 
  of 
  an 
  inch 
  in 
  diameter. 
  This 
  very 
  common 
  injury 
  is 
  

   most 
  frequently 
  done, 
  according 
  to 
  our 
  observation, 
  by 
  the 
  larvae 
  and 
  

   adults 
  of 
  this 
  common 
  flea-beetle 
  of 
  the 
  beet. 
  The 
  adult 
  insect 
  is 
  about 
  

   a 
  quarter 
  of 
  an 
  inch 
  long, 
  steel-blue 
  to 
  blackish 
  above, 
  with 
  pale 
  yellow 
  

   thorax 
  without 
  spots; 
  the 
  larva 
  is 
  grayish 
  white, 
  cylindrical 
  in 
  general 
  

   form, 
  and 
  also 
  about 
  a 
  quarter 
  of 
  an 
  inch 
  long. 
  The 
  segments 
  are 
  

   strongly 
  marked, 
  each 
  bearing 
  a 
  row 
  of 
  raised 
  tubercles, 
  with 
  a 
  stiff 
  

   black 
  hair 
  from 
  the 
  tip 
  of 
  each 
  tubercle. 
  The 
  larvae 
  commonly 
  feed 
  

   from 
  the 
  under 
  side 
  of 
  the 
  leaf, 
  and 
  drop 
  to 
  the 
  ground 
  when 
  disturbed. 
  

   When 
  young 
  they 
  merely 
  gnaw 
  the 
  surface, 
  causing 
  discolored 
  spots 
  to 
  

   appear 
  on 
  the 
  upper 
  side, 
  but 
  when 
  older 
  they 
  eat 
  entirely 
  through 
  the 
  

   leaf. 
  They 
  are 
  somewhat 
  gregarious, 
  especially 
  when 
  young, 
  keeping 
  

   together 
  and 
  moving 
  in 
  company 
  from 
  one 
  leaf 
  to 
  another. 
  

  

  The 
  species 
  ranges 
  from 
  the 
  Rocky 
  Mountains 
  to 
  the 
  Atlantic 
  and 
  

   Gulf 
  coast, 
  and 
  is 
  also 
  reported 
  from 
  Montana 
  and 
  British 
  America. 
  

   It 
  has 
  been 
  treated 
  as 
  a 
  spinach 
  insect, 
  attacking 
  this 
  plant 
  as 
  it 
  does 
  

   the 
  beet, 
  and 
  the 
  beetles 
  have 
  been 
  found 
  feeding 
  on 
  lamb's-quarters, 
  

   pigweed, 
  and 
  a 
  species 
  of 
  chickweed 
  {Stellaria 
  media). 
  

  

  There 
  seem 
  to 
  be 
  two 
  broods 
  in 
  a 
  season. 
  The 
  female 
  beetles 
  

   emerge 
  from 
  their 
  winter 
  quarters 
  in 
  April 
  and 
  May, 
  and 
  lay 
  their 
  eggs 
  

   in 
  those 
  months 
  and 
  in 
  early 
  June 
  at 
  the 
  bases 
  of 
  the 
  plants 
  infested, 
  on 
  

   bits 
  of 
  leaf 
  or 
  earth, 
  or 
  even 
  within 
  the 
  earth. 
  The 
  eggs 
  are 
  orange- 
  

   colored, 
  and 
  placed 
  on 
  end 
  like 
  those 
  of 
  the 
  potato 
  beetle. 
  They 
  

   begin 
  to 
  hatch 
  in 
  April 
  or 
  May, 
  according 
  to 
  locality, 
  and 
  continue 
  to 
  

   hatch 
  into 
  June 
  and 
  even 
  into 
  early 
  July. 
  Most 
  of 
  the 
  larvre 
  of 
  this 
  

   generation 
  have 
  attained 
  their 
  growth 
  and 
  entered 
  the 
  earth 
  for 
  pupa- 
  

   tion 
  late 
  in 
  June 
  and 
  early 
  in 
  July, 
  and 
  beetles 
  begin 
  to 
  emerge 
  in 
  about 
  

   a 
  month 
  from 
  the 
  time 
  of 
  the 
  first 
  deposit 
  of 
  the 
  eggs. 
  Eggs 
  deposited 
  

   June 
  2oth 
  at 
  Urbana 
  gave 
  origin 
  to 
  the 
  adult 
  July 
  25th, 
  and 
  others 
  ob- 
  

   tained 
  June 
  27th 
  and 
  28th 
  yielded 
  larv?e 
  which 
  began 
  to 
  pupate 
  July 
  

   15th 
  and 
  to 
  yield 
  adults 
  July 
  25th. 
  The 
  beetles 
  of 
  the 
  second 
  genera- 
  

   tion 
  lay 
  their 
  eggs 
  in 
  late 
  July, 
  August, 
  and 
  early 
  September, 
  and 
  the 
  

   beetles 
  of 
  this 
  second 
  brood 
  mature 
  before 
  winter 
  sets 
  in. 
  Miss 
  Murt- 
  

   feldt 
  has 
  found 
  the 
  larvje 
  feeding 
  upon 
  spinach 
  leaves 
  near 
  St. 
  Louis 
  in 
  

   April 
  and 
  May, 
  the 
  first 
  beetles 
  from 
  these 
  larvce 
  appearing 
  late 
  in 
  the 
  

   latter 
  month. 
  In 
  the 
  northern 
  half 
  of 
  Illinois 
  the 
  development 
  is 
  some- 
  

  

  