570 
JOURNAL  OF  HORTICULTURE  AND  COTTAGE  GARDENER. 
December  28,  1899, 
but  the  “  Hand-list  of  Trees  and  Shrubs  ”  names  it  as  a  distinct 
species.  As  grown  in  gardens  it  appears  to  be  distinct. 
*»  Yucca  aloifolia  is  (principally  by  its  variegated  varieties)  well 
known  in  glass  structures.  The  green-leaved  or  typical  plant  is 
worth  growing  in  places  which  are  not  too  cold,  and  where  it  can 
receive  some  shelter.  Its  hardiness  is  affirmed  by  some  to  be  beyond 
doubt,  but  one  would  hesitate  to  agree  with  this  so  far  as  it  refers  to 
cold  localities. 
There  are  a  good  many  other  Yuccas,  among  which  may  be 
named  Y.  Whipplei,  a  good  hardy  plant ;  Y.  angustifolia,  the  dwarfest, 
which  is  seldom  more  than  3  feet  in  height  ;  and  Y.  Treculeana,  which 
is  of  noble  habit  and  soon  grows  to  a  great  size.  The  individual 
flowers  of  the  Yuccas  bear  a  considerable  resemblance  to  each  other, 
and  are  generally  of  a  yellowish  white  colour,  so  that  I  have  considered 
it  needless  to  mention  them  in  detail. 
it  may  be  added  that  seeds  of  several  species  are  obtainable,  and 
that  they  are  easily  raised  from  seeds  if  these  are  fresh.  They  ought 
to  be  sown  and  grown  under  glass.  A  needful  reminder  is  that 
slugs  are  fond  of  seedling  Yuccas.  Much  more  might  be  said  regarding 
the  value  and  uses  of  these  plants,  but  the  notes  given  may  serve  to 
bring  them  before  those  desiring  plants  of  like  habit. — A. 
CINERARIA  FLY,  OR  MARGUERITE  FLY 
(PHYTOMYZA  NIGRICORNIS). 
5^  It  was  noticed  some  years  back  that  many  of  the  Marguerite  and 
Cineraria  plants  in  the  gardens  round  Wellington  were  marked,  as 
though  tiny  snails  had  crawled  over  them,  leaving  white  tracks 
behind.  A  further  examination,  however,  showed  that  the  damage 
was  not  on  the  surface  of  the  leaves,  but  had  been  caused  by  a  small 
grub,  or,  rather,  numerous  small  grubs,  tunnelling  between  the  two 
surfaces,  and  eating  out  the  flesh  in  all  directions.  Later  on  these 
grubs  turned  to  chrysalids,  and  from  them  emerged  tiny  flies,  which 
to  the  unaided  eye  look  black,  but  which  the  microscope  shows  are 
somewhat  highly  coloured. 
The  insect  subsequently  greatly  extended  its  field  of  operations, 
until  there  is  scarcely  a  garden,  or  indeed  a  roadside,  where  it  may 
not  be  seen.  Cineraria  growers  suffer  most  from  its  depredations.  The 
eggs  are  usually  laid  on  the  under  side  of  the  leaf,  but  at  times  the 
females  seem  careless,  and  place  them  on  either  upper  or  lower  surface, 
and  sometimes  on  the  stem. 
The  period  elapsing  before  the  eggs  hatch  varies  with  the  position 
of  the  plant,  and  apparently  is  longer  or  shorter  according  to  the 
amount  of  light  and  warmth  received.  Some,  in  one  experimental 
shade,  hatched  five  days  after  bemg  laid,  and  others  were  double  that 
time.  Shortly  after  the  young  grubs  appear,  the  leaves,  if  carefully 
examined,  will  be  found  to  have  small  dots  where  the  grubs  have 
eaten  through  the  epidermis,  and  from  these  dots  the  mines  will 
extend  in  all  directions,  crossing  and  recrossing  till  in  many  cases 
nothing  but  the  cuticle  remains.  The  leaves,  of  course,  soon  wither 
and  die.  Before  this  occurs  the  grubs  have  reached  maturity,  eaten 
close  to  the  surface,  and  entered  the  chrysalis  state.  The  mines  are  of 
course  in  places  partly  filled  with  the  excreta  of  the  grubs,  but  at 
various  points  will  be  seen  larger  objects,  some  greenish,  others  brown, 
and  others  black.  These  are  the  chrysalids,  and  in  favourable  weather 
the  flies  will  emerge  in  about  a  week  after  the  chrysalids  have  assumed 
the  last-mentioned  colour. 
The  above  cuts  will  give  a  good  idea  of  the  form  of  both  grub 
and  fly.  The  latter  will  well  repay  the  trouble  of  microscopic 
examination.  The  colour  of  the  body  varies  from  rich  black  to  slate 
colour;  the  head  is  ochreous,  with  a  greenish -yellow  spot  on  the 
crown.  The  poisers  and  thighs  are  yellowish,  and  the  wonderfully 
iridescent  wings  make  this  insect  a  most  beautiful  object  under  a 
moderate  power. 
It  is  a  species  of  Phvtomyza  (evidently  closely  allied  to 
P.  nigricornis),  a  genus  the  members  of  which  are  notorious  for  dis¬ 
figuring  garden  plants. 
[Since  the  above  was  written,  I  have  received  from  Mr.  C.  French, 
Government  Entomologist,  Victoria,  a  note  in  which  he  says  that 
specimens  sent  by  me  have  been  submitted  to  Mr.  Skuse,  who  pro¬ 
nounces  them  undoubtedly  P.  nigricornis.] 
The  difficulties  encountered  in  fighting  this  pest  would  not  be  so 
great  were  its  attacks  confined  to  garden  plants — namely,  Cinerarias, 
Peas  and  Chrysanthemums — but  unfortunately  it  is  found  on  a 
number  of  wild  plants  also.  I  have  reared  specimens  from  Groundsel, 
Meliolotus,  and  the  recently-introduced  Noogora  burr,  while  the 
common  Sow-Thistle  or  Eauriki  is  everywhere  attacked,  and  seems  to 
be  the  favourite  food  plant. 
I  have  taken  flies  reared  on  Cinerarias  and  placed  some  in  a 
breeding  cage  with  Rauriki,  and  others  in  a  separate  cage  with 
Cineraria.  The  progeny  of  the  former  throve  much  better  than  the 
others. 
The  insects  being  miners,  it  is  very  difficult  to  get  at  them  when 
once  the  plant  is  attacked ;  defensive  rather  than  offensive  measures 
must  therefore  be  employed. 
In  greenhouses  the  plants  should  be  carefully  watched  at  the 
commencement  of  an  attack,  and  all  affected  leaves  picked  off  and 
burned.  If  a  plant  is  set  in  a  tub  of  water,  so  that  the  leaves  are 
immersed,  and  left  there  for  some  hours,  it  will  be  found  that  many  of 
the  grubs  have  come  to  the  entrance  of  the  mines  and  been  drowned. 
This,  of  course,  will  not  kill  the  chrysalids. 
The  above  plan  caunot  be  adopted  with  outdoor  plants,  but  I  have 
proved  experimentally  that  the  female  will  not  lay  her  eggs  on  a 
plant  which  has  been  carefully  sprayed  with  arsenical  spray  or  with 
tar  water  (£  lb.  coal  tar,  boiled  in  1  gallon  of  water,  and,  when  boiled 
for  some  time,  diluted  with  50  gallons  fresh  water.  This  must  be 
stirred  till  well  mixed ;  it  is  then  ready  for  use.  Tar  is  obnoxious  to 
Fig,  101.— Cineraria  orJVIarguerite  Fly  (Phytomyza 
nigricornis). 
1,  Leaf  of  Cineraria,  showing  damage  done  by  the  mining  of  the  larva  (from 
nature);  2,  Grub,  magnified;  3,  Chrysalis,  natural  size;  4,  JFly,  magnified. 
(2  and  4  after  Westwood). 
all  insects,  and  they  will  get  away  from  it  if  possible),  preferring  to 
deposit  them  on  the  glass  sides  of  the  breeding  cage.  This  remedy 
has  been  thoroughly  tested,  and  has  proved  quite  successful. 
This  spraying  will  certainly  need  repeating  from  time  to  time,  as 
the  insect  is  a  very  free  breeder.  Indeed,  I  have  some  specimens  of 
the  third  generation  now  in  breeding  cages. 
In  Europe  there  is  a  small  ichneumon  fly  which  helps  to  keep 
P.  nigricornis  in  check.  This  has  now  reached  the  colony,  but  is  not 
a  sufficiently  effective  check  to  be  relied  on  solely. — [ New  Zealand 
Department  of  Agriculture.  Leaflets  for  Gardeners  and  Fruit 
Groivers,  No.  4.] 
LATE  SPRING  PLANTING. 
For  all  classes  of  fruit  and  other  deciduous  trees  there  is  no 
question  whatever  that  early  autumn  planting  or  just  as  the  leaves 
are  turning  preparatory  to  falling  is  the  best  of  all  times  to  transplant. 
The  soil  has  still  much  of  latent  summer  heat  in  it,  and  usually  rain 
will  soon  follow  in  sufficient  quantity  to  make  planting  easy  even  on 
heavy  soils  by  the  middle  of  October.  The  roots  if  carefully 
trimmed  start  again,  and  the  trees  before  midwinter  will  be  semi- 
established. 
But  it  is  not  possible  to  get  all  planting  done  in  autumn,  and  as 
a  makeshift  spring  planting  has  to  take  its  place.  To  make  the  best 
of  a  poor  job  this  should  be  left  until  root  action  has  again  com¬ 
menced,  and  the  buds  on  the  trees  are  beginning  to  move.  This  will 
be  found  much  more  satisfactory  than  planting  in  early  spring,  and  I 
have  repeatedly  proved  the  truth  of  this.  I  planted  during  the 
spring  of  1899  a  large  number  of  deciduous  shrubs  in  an  exposed 
border,  when  the  growth  was  very  forward,  and  flower  buds  in  some 
cases  were  showing.  Acers,  Rubus,  Prunus,  Pyrus,  Deutzias,  Lilacs, 
Oytisus  and  many  others  were  included,  and  it  was  very  successful, 
hardly  a  plant  perishing.  Had  these  been  planted  a  month  earlier 
there  would  have  been  a  different  tale  to  tell. — H.  R.  R. 
