April  29,  1897 
JOURNAL  OF  HORTICULTURE  AND  COTTAGE  GARDENER. 
369' 
THE  ONION  FLY  (PHORBIA  CEPETORUM),  MEADE. 
The  Onion  fly  causes  serious  injuries  to  the  Onion  crop  in  some 
seasons,  and  it  appears  to  be  on  the  increase  in  this  country.  It  is  also 
a  source  of  great  trouble  to  the  Onion  growers  in  the  United  States,  and 
in  continental  countries.  Frequently  in  English  market  gardens  and 
market  garden  farms,  where  Onions  are  extensively  cultivated,  large 
per-centages  of  the  plants  are  quite  spoiled  by  the  attacks  of  this  fly. 
In  cottage  gardens  and  allotments  the  whole  of  the  plants  on  the  small 
Onion  beds  of  the  cultivators  are  often  ruined  by  successive  generations 
of  this  insect. 
The  first  indications  of  the  infestation  are  shown  by  the  longest  or 
first  leaves  of  the  Onion  plants  becoming  yellow,  and  afterwards  whitish  ; 
if  these  are  pulled  they  come  easily  away  frcm  the  stem,  and  gradually 
the  other  leaves  become  yellow  and  decay.  The  bulb  will  be  found  to 
be  small  and  badly  shaped,  and  having  yellowish  maggots  within  its 
folds,  feeding  upon  it,  and  eventually  causing  it  to  become  rotten  and 
useless. 
In  other  cases,  the  outer  or  lower  leaves  of  the  plants  are  seen  to  be 
lying  on  the  ground,  still  green,  while  the  leaves  remaining  upright  and 
green  feel  soft  and  flabby. 
If  infested  plants  are  examined  it  will  be  generally  noticed  that  in 
the  case  of  very  young  plants  they  are  nearly  eaten  through,  just  above 
the  swelling  bulbs,  by  the  maggots  or  larvae  of  the  fly.  In  older  plants, 
with  large  bulbs,  maggots  of  all  ages  and  sizes  will  be  found  within  the 
bulbs. 
Onion  plants  that  become  yellow  and  show  signs  of  drooping  should 
be  examined  for  maggots  just  below  the  surface  of  the  ground. 
Life  History. 
The  male  and  female  flies  of  this  species  differ  slightly.  The  male  is 
dark  grey  in  colour,  with  black  bristles.  The  eyes  are  red  and  close 
together.  Upon  the  thorax  are  four  bright  brown  Btripes  and  four  rows 
of  black  bristles.  The  abdomen  is'  ash-coloured,  rather  narrow,  having 
triangular  black  spots  down  it  which  almost  join  each  other.  The  legs 
are  pitchy. 
In  colour  the  female  fly  closely  resembles  the  male,  but  the  abdomen 
is  dark  grey,  with  the  end  more  pointed  than  in  the  male  ;  and  the  eyes 
are  wide  apart. 
From  six  to  eight  eggs  are  laid  on  an  Onion  plant,  upon  the  leaves 
and  just  above  the  ground.  The  eggs,  which  are  white,  long,  and  some¬ 
what  oval,  can  be  easily  seen  without  a  glass.  Maggots  (larvae)  come 
from  the  eggs  in  from  five  to  seven  days,  according  to  the  temperature 
and  other  conditions,  and  make  burrows  down  into  the  rout,  or  bulb, 
between  the  sheathing  leaves.  They  feed  upon  the  contents  of  the 
cylindrical  root  which  can  hardly  at  this  stage  be  styled  a  bulb,  and 
move  on  to  other  plants.  Later  on,  when  the  bulbs  are  larger,  they  are 
occupied  by  many  maggots,  which  feed  on  them  and  cause  them  to 
become  rotten.  Sometimes  the  bulbs  will  be  seen  to  be  swarming  with 
maggots,  and  the  earth  round  them  is  also  infested.  The  maggot  con¬ 
tinues  in  the  larval  state  for  a  period  varying  from  thirteen  to  fifteen 
days,  feeding  throughout  this  period  upon  the  Onion  roots  or  bulbs.  It 
is  nearly  four  lines  (one-third  of  an  inch)  in  length,  dull  yellowish 
white,  or  dirty  white,  in  colour.  The  head  part  of  its  body  is  sharply 
pointed,  and  the  head,  furnished  with  a  pair  of  black  hooks,  can  be 
extended  at  will  ;  the  tail  end  is  cut  off  obliquely  flat,  and  in  the  centre 
there  are  two  brown  spiracles  or  breathing  tubes,  and  on  the  margin  of 
the  flat  tail  end  there  are  eight  teeth  or  projections. 
Before  pupation  takes  place  the  maggot  usually  goes  into  the  earth. 
Sometimes  pupation  occurs  within  the  Onions.  The  pupa,  or  rather  the 
pupa  case  or  puparium,  Is  chestnut  brown,  oval,  not  so  long  as  the 
maggot,  and  has  the  same  toothlike  projections  on  the  caudal  end.  On 
opening  this  puparium  the  white  pupa  will  be  seen  with  the  embryonic 
wings  of  the  future  fly,  which  appears  in  from  thirteen  to  sixteen  days 
after  pupation. 
There  are  several  generations  of  this  insect.  The  first  has  been  seen 
as  early  as  the  25th  of  April  in  very  forward  seasons,  and  flies  have  been 
noticed  through  the  autumn  and  as  late  as  November.  Curtis  states, 
however,  that  he  saw  them  alive  in  December. 
Methods  of  Prevention  and  Remedies. 
Spraying  Onion  plants  with  offensive  compositions  is  a  good  way  of 
preventing  infestation.  Paraffin  emulsion  is  as  good  a  compound  as  any 
for  this  purpose.  It  may  be  made  by  thoroughly  mixing  together  3  pints 
of  paraffin  and  ^  lb.  of  softsoap  with  1  gallon  of  boiling  water.  Mixing 
may  be  done  by  passing  the  composition  through  a  hand  pump  once  or 
twice  ;  6  gallons  of  water  should  be  added  to  dilute  it  sufficiently,  so  as 
not  to  burn  tbe  Onion  leaves.  When  the  Onion  leaves  are  young  and 
very  tender  7  or  8  gallons  should  be  added.  It  may  be  applied  on 
small  plot*  of  Onions  with  a  Knapsack  machine  ;  on  large  breadths  with 
a  horse  distributing  machine.  The  spray  should  be  dense  and  in  the 
form  of  mist.  This  operation  should  be  performed  early  in  the  season, 
when  the  Onions  have  established  their  leaves. 
Spraying  must  be  repeated,  probably  twice  or  thrice,  especially  if 
heavy  showers  fall  after  the  process. 
When  Onion  plants  in  a  field  or  garden  are  noticed  to  droop  and 
wither  all  such  plants  should  be  taken  up  and  burnt  or  deeply  buried. 
They  must  be  taken  up  by  means  of  a  little  three-pronged  fork,  or  some 
other  handy  tool,  so  that  every  particle  of  bulb  and  leaf  is  removed. 
Wherever  it  is  possible  Onions  should  not  be  grown  again  for  at 
least  one  season  on  land  where  this  crop  has  been  infested,  as  the  pupae 
remain  in  the  ground  during  me  wiuter.  All  pieces  of  bulbs  should  be 
got  off  infested  land,  as  pupae  occasionally  remain  in  the  bulbs.  If  it 
is  necessary  to  take  two  successive  crops  of  Onions  on  infested  land  the 
ground  should  be  dug  very  deeply,  two  spits  deep,  and  well  limed  or 
gas-limed. 
Sprinkling  the  young  Onions  with  soot  has  been  adopted  with  some 
advantage  ;  but  the  pungent  odour  soon  evaporates,  and  it  is  necessary 
to  give  several  dressings. 
Kainit,  broadcasted  on  land  cropped  with  Onions  at  the  rate  of  5  cwt. 
per  acre,  has  been  found  to  be  of  great  use.  The  action  of  kainit  as  a 
preventive  of  some  kinds  of  insect  attack  in  larval  form  has  been 
often  noticed,  though  it  is  rather  difficult  to  define  the  form  or  nature 
of  its  action.  In  the  case  of  the  Onion  maggots  it  would  appear  that 
kainit  prevents  their  progress  from  one  Onion  to  another,  either  by  the 
shape  of  its  crystals  or  by  some  pungent  emanation  from  it.  It  is  not 
the  stimulus  that  it  gives  to  plants  which  make  them  grow  away  from 
their  enemies,  as  kainit.is  not  by  any  means  a  forcing  manure.  Kainit 
should  be  hoed  very  lightly  in  after  it  has  been  broadcasted  on. 
Nitrate  of  soda,  applied  at  the  rate  of  to  2  cwt.  per  acre,  should  be 
Fig.  76.— a  and  b.  Larva,  natural  size  and  magnifled;  c  and  d,  Pupi,  natural  size  and 
magnified  ;  e,  Fly  magnifled ;  lines  showing  wing  expanse  and  length  of  body. 
put  on  infested  land  in  order  to  stimulate  the  plants  and  make  them 
grow  away  from  the  enemy. 
Lime  and  soot,  mixed  together  in  the  proportion  of  1  bushel  of  soot 
to  2  bushels  of  lime,  very  finely  powdered  and  broadcasted  over  the 
infested  plants,  and  lightly  hoed  in,  has  been  efficacious  in  a  degree. — 
( Board  of  Agriculture  Leaflet,  No.  31.) 
EVOLUTIONARY  ESSAYS. 
Evolution  was  once  a  terrible  word  to  many,  and  amongst  these 
some  of  the  ablest  and  best  of  men  who  save  thought,  all  of  them 
perhaps  not  the  most  profound,  to  the  subject.  Not  a  few  of  these, 
however,  in  time  came  to  regard  evolution  as  not  such  an  outrageous 
thesis  after  all,  but  as  something  associated  with  one  of  the  first  laws  of 
Nature — growth,  or  in  other  words  steady  advancement,  gradual,  imper¬ 
ceptible  progress,  like  the  growth  of  a  tree  from  its  seed,  but  culminating 
in  a  change  not  less  marvellous  than  tangible  and  indisputable.  Let  no 
one,  then,  be  frightened  by  the  once  dread  word  of  evolution,  because 
in  reality  its  significance  is  apparent  everywhere  in  the  animal,  vegetable, 
and  mineral  kingdom. 
In  “Evolutionary  Essays”  we  merely  condense  the  sub-title, 
indicating  the  nature  of  an  American  work,  of  which  the  chief  and 
formal  title  is  the  “  Survival  of  the  Unlike,”  a  sort  of  parody,  we  may 
almost  venture  to  say,  on  another  formula  not  unfamiliar — namely,  the 
“  Survival  of  the  Fittest.” 
The  author  of  this  work — which  we  have  had  in  hand  for  a  consider¬ 
able  time,  but  which,  owing  to  pressure  on  space,  could  not  be  sooner 
referred  to — is  Mr.  L.  H.  Bailey  of  the  Cornell  University,  Ithaca,  New 
York.*  We  venture  to  say  that  no  one  knows  better  than  the  author  of 
this  volume  of  over  500  pages  that  the  title  he  has  chosen  embodies  a 
mere  truism.  No  one  knows  better  than  he  that  variety,  or  exact 
unlikeness,  meets  us  everywhere.  No  two  individuals  can  be  Baid  with 
accuracy  to  be  precisely  alike  in  respect  to  appearance,  habits,  and 
influences  ;  no  two  men,  animals,  plants,  trees,  leaves,  or  flowers  can  be 
said  to  be  absolutely  identical.  There  are  divergencies  more  or  less 
apparent,  but  all  the  same  existent,  though  in  some  instances  the  micro¬ 
scope  may  be  necessary  to  reveal  them.  This  being  so,  it  may  be  con¬ 
ceded  that  Mr.  Bailey  has  chosen  his  title  wisely,  because  under  it  may 
be  written  essays  on  almost  every  conceivable  subject  connected  with 
animal  and  plant  life  ;  but  it  is  not  everyone  to  whom  it  is  given  to 
write  so  lucidly,  and  it  may  be  said  bo  logically,  as  the  author  of  this 
volume  before  us  The  work  comprises,  as  is  stated  on  the  title  page,  a 
“  Collection  of  Evolutionary  Essays  Suggested  by  a  Study  of  Domestic 
Plants.”  It  seems  to  be  composed  of  some  thirty  lectures  delivered  at 
mote  or  lees  wide  intervals,  and  though  there  is  something  of  interest  in 
most  of  them  it  can  scarcely  be  said  that  complete  harmony  pervades 
the  whole  ;  indeed,  it  is  hard  to  exercise  the  suspicion  that  an  obviously 
able  man  could  not  wholly  resist  on  all  occasions  the  temptation  of  what 
is  known  on  “  this  side  ”  in  homely  vernacular  as  padding  ;  yet  let  it 
be  said  that  the  handbook  as  a  whole  is  well  worth  reading. 
We  have  no  particular  inclination  to  criticise,  adversely  or  otherwise, 
the  theories  of  the  author  or  his  methods  of  treating  the  multitudinous 
*  The  Macmillan  Company,  Bedford  Street,  Oovent  Garden,  London. 
