﻿PACKARD.] 
  THE 
  ONION-FLY. 
  741 
  

  

  whereby 
  some 
  of 
  the 
  flies 
  are 
  liable 
  to 
  be 
  always 
  present 
  in 
  the 
  garden, 
  

   in 
  readiness 
  to 
  deposit 
  their 
  eggs; 
  and 
  maggots 
  of 
  widely-different 
  sizes 
  

   are 
  commonly 
  met 
  with 
  in 
  the 
  same 
  onion. 
  

  

  "The 
  eggs 
  or 
  'fly-blows' 
  are 
  loosely 
  placed 
  upon 
  the 
  onion 
  slightly 
  

   above 
  the 
  surface 
  of 
  the 
  ground 
  (Fig. 
  — 
  ), 
  some 
  of 
  them 
  being 
  dropped 
  

   along 
  the 
  thin 
  edge 
  of 
  the 
  sheath 
  or 
  white 
  membranous 
  collar, 
  which 
  is 
  

   formed 
  by 
  the 
  base 
  of 
  the 
  lower 
  leaf 
  clasping 
  around 
  the 
  stalk, 
  and 
  

   others 
  are 
  crowded 
  into 
  the 
  crevices 
  between 
  the 
  bases 
  of 
  the 
  leaves, 
  

   slightly 
  above 
  where 
  they 
  issue 
  from 
  this 
  sheath. 
  From 
  two 
  to 
  six 
  or 
  

   more 
  eggs 
  are 
  usually 
  placed 
  on 
  particular 
  plants 
  here 
  and 
  there 
  through 
  

   the 
  bed. 
  They 
  are 
  perceptible 
  to 
  the 
  eye, 
  being 
  white 
  and 
  smooth, 
  

   four-hundredths 
  of 
  an 
  inch 
  (0.04) 
  long, 
  and 
  a 
  fourth 
  as 
  thick, 
  and 
  of 
  an 
  

   oval 
  form." 
  When 
  the 
  minute 
  maggot 
  hatches 
  from 
  the 
  egg, 
  it 
  works 
  

   its 
  way 
  downward 
  inside 
  of 
  the 
  sheath, 
  its 
  track 
  being 
  marked 
  by 
  a 
  

   slender, 
  discolored 
  streak, 
  till 
  it 
  reaches 
  the 
  root, 
  on 
  which 
  it 
  feeds 
  "till 
  

   it 
  is 
  wholly 
  consumed, 
  only 
  the 
  thin 
  outer 
  skin 
  remaining. 
  After 
  eating 
  

   the 
  bulb 
  of 
  one 
  plant 
  they 
  attack 
  the 
  next, 
  until 
  sometimes 
  a 
  third 
  or 
  

   a 
  half 
  of 
  the 
  bed 
  is 
  destroyed. 
  

  

  The 
  first 
  indication 
  that 
  the 
  plant 
  has 
  been 
  attacked 
  is 
  afforded 
  by 
  

   the 
  leaves 
  turning 
  yellow 
  and 
  wilting. 
  "On 
  carefully 
  digging 
  up 
  and 
  

   examining 
  the 
  affected 
  plant, 
  if 
  it 
  is 
  young 
  and 
  the 
  root 
  small 
  and 
  

   cylindrical, 
  we 
  commonly 
  find 
  it 
  completely 
  cut 
  asunder 
  as 
  represented 
  

   in 
  Fig. 
  — 
  , 
  only 
  the 
  thin 
  outer 
  skin 
  remaining, 
  whereby 
  the 
  slightest 
  pull- 
  

   ing 
  upon 
  the 
  top 
  draws 
  it 
  up 
  out 
  of 
  the 
  ground. 
  Later 
  in 
  the 
  season, 
  

   when 
  the 
  round 
  bulb 
  is 
  beginning 
  to 
  be 
  formed, 
  as 
  in 
  Fig. 
  — 
  , 
  we 
  find 
  a 
  

   hole 
  perforated 
  in 
  its 
  side, 
  opening 
  into 
  a 
  cavity 
  in 
  the 
  interior, 
  and 
  the 
  

   earth 
  around 
  this 
  perforation 
  is 
  wet 
  and 
  slimy, 
  forming 
  a 
  mass 
  of 
  filthy 
  

   mud 
  in 
  which 
  those 
  worms 
  are 
  lying 
  which 
  are 
  not 
  engaged 
  in 
  feeding. 
  

   And 
  by 
  this 
  interior 
  cavity 
  the 
  central 
  leaves 
  of 
  the 
  plant 
  are 
  severed 
  

   from 
  their 
  connection 
  with 
  the 
  fibrous 
  rootlets, 
  as 
  shown 
  in 
  the 
  figure, 
  

   whereby 
  it 
  is 
  now 
  these 
  central 
  and 
  not 
  the 
  outer 
  leaves 
  which 
  first 
  

   turn 
  yellow 
  and 
  die, 
  and 
  all 
  the 
  upper 
  portion 
  of 
  the 
  root 
  soon 
  becomes 
  

   soft 
  and 
  putrid, 
  while 
  the 
  bottom 
  part, 
  continuing 
  to 
  be 
  nourished 
  by 
  

   the 
  fibrous 
  rootlets, 
  remains 
  sound, 
  and 
  the 
  worms 
  now 
  crowd 
  into 
  this 
  

   part 
  to 
  feed, 
  whereby 
  it 
  sometimes 
  presents 
  a 
  wonderful 
  appearance, 
  

   being 
  thronged 
  with 
  worms 
  wedged 
  together 
  side 
  by 
  side 
  in 
  a 
  compact 
  

   mass, 
  all 
  with 
  their 
  heads 
  downward, 
  eagerly 
  consuming 
  the 
  last 
  

   remains 
  of 
  food 
  there 
  is 
  there, 
  and 
  only 
  the 
  rounded 
  hind 
  ends 
  of 
  their 
  

   bodies 
  exposed 
  to 
  view, 
  these 
  forming 
  an 
  even 
  surface 
  similar 
  to 
  the 
  

   cobble-stones 
  of 
  a 
  street-pavement, 
  as 
  represented 
  in 
  Fig. 
  — 
  ." 
  

  

  The 
  maggot 
  attains 
  its 
  growth, 
  in 
  summer, 
  in 
  about 
  a 
  fortnight^ 
  and 
  

   changes 
  to 
  a 
  pupa 
  either 
  in 
  the 
  cavity 
  in 
  the 
  onion 
  or 
  in 
  "the 
  wet, 
  slimy 
  

   earth 
  which 
  is 
  in 
  contact 
  with 
  the 
  onion. 
  It 
  here 
  ceases 
  to 
  move, 
  it 
  

   becomes 
  contracted 
  and 
  shorter 
  in 
  length, 
  its 
  skin 
  hardens 
  and 
  changes 
  

   to 
  a 
  tarnished 
  yellow 
  and 
  finally 
  to 
  a 
  chestnut 
  color 
  with 
  a 
  stain 
  of 
  

   black 
  at 
  each 
  end." 
  This 
  is 
  the 
  pupa-case, 
  and 
  the 
  true 
  pupa 
  is 
  inside. 
  

   In 
  this 
  condition 
  it 
  lies 
  about 
  two 
  weeks 
  before 
  the 
  fly 
  escapes. 
  

  

  In 
  Essex 
  County, 
  Massachusetts, 
  this 
  fly 
  is 
  very 
  destructive. 
  The 
  

   maggots 
  appear 
  about 
  the 
  middle 
  and 
  last 
  of 
  May, 
  and 
  by 
  the 
  third 
  

   week 
  in 
  August 
  the 
  larvse 
  are 
  not 
  found, 
  only 
  the 
  pupa-cases. 
  

  

  Description. 
  — 
  The 
  larva 
  or 
  maggot 
  is 
  eliiniug, 
  dull 
  white, 
  cylindrical, 
  tapering 
  to 
  a 
  

   poiut 
  in 
  front, 
  and 
  when 
  crawling 
  and 
  elongated, 
  nearly 
  the 
  whole 
  length 
  of 
  the 
  body 
  

   becomes 
  tapering. 
  At 
  the 
  forward 
  end 
  the 
  jaws 
  appear 
  under 
  the 
  skin 
  as 
  a 
  short 
  black 
  

   stripe. 
  The 
  hind 
  end 
  is 
  cut 
  off 
  abruptly 
  in 
  an 
  oblique 
  direction, 
  forming 
  a 
  flattened 
  

   Burl'ace, 
  on 
  whicli, 
  slightly 
  above 
  the 
  center, 
  are 
  two 
  elevated 
  dots 
  of 
  a 
  cinnamou-brown 
  

   color, 
  and 
  appearing 
  somewhat 
  like 
  a 
  pair 
  of 
  eyes; 
  and 
  around 
  the 
  margin 
  are 
  eight 
  

   small 
  projecting 
  teeth, 
  of 
  which 
  the 
  two 
  lowest 
  ones 
  are 
  largest 
  ; 
  and 
  a 
  little 
  forward 
  

  

  