July  JS,  1890. 
JOURNAL  OF  HORTICULTURE  AND  COTTAGE  GARDENER. 
79 
labour  involved  is  enormous,  and  few  indeed  are  the  places  where 
it  ii  freely  supplied. 
Nevertheless,  although  it  may  not  be  possible  to  give  sufficient 
attention  to  produce  the  highest  results,  with  effort  and  judgment 
we  mostly  manage. to  avoid  disaster — manage  to  prevent  the  occur¬ 
rence  of  gaps  in  flower  beds  and  shrubberies,  or  breaks  in  the 
chain  of  supply  of  flowers,  fruits,  and  vegetables — it  is  towards  the 
attainment  of  these  objects  that  our  main  efforts  should  be  directed. 
Afternoon  and  evening  waterings  are  much  more  beneficial  than 
those  given  at  other  times,  simply  because  the  water  sinks  into  the 
soil,  and  has  time  to  become  thoroughly  absorbed  by  it  before  the 
lun  commences  to  draw  it  out  again  :  but  it  is  often  necessary  to 
continue  watering  throughout  the  day.  When  this  is  so  much  can 
be  done  to  make  the  best  of  unfavourable  circumstances  by 
following  the  sun’s  course,  and  watering  in  aspects  that  it  has  just 
left,  for  during  every  part  of  the  day  there  is  generally  some  part 
of  the  garden  that  is  comparatively  shady. 
It  may  be — I  hope  it  will— that  before  these  lines  appear  in 
print  the  much-needed  rain  will  have  fallen.  If  so,  perhaps  some 
will  think  these  notes  “  as  a  reminder  ”  of  but  little  value.  I 
must  counsel  them,  however,  not  to  be  too  hasty  in  their  judgment. 
August  and  September  are  often  “scorching”  months.  Mulching 
may  still  be  continued  with  advantage,  and  I  fear  that  much 
watering  will  yet  have  to  be  done  this  season. — D.  W.  0. 
APHIDES. 
The  insects  known  as  aphides  or  plant  lice  belong  to  the  order  of 
Tnsecta,  called  Hemiptera.  Mouth  suctorial,  beak-shaped ;  rostrum 
jointed,  elongated,  forming  a  tubular  sheath  for  the  needle-shaped 
maxillae  and  mandibles  ;  wings  four,  naked,  membranous,  but  they  may 
be  absent  or  reduced  to  two,  as  in  the  male  scale  insects. 
Aphidm  or  plant  lice  comprise  about  300  British  spdcies,  all  of  which 
feed  on  the  juices  of  plants,  and  are  found  in  every  garden,  field,  and 
forest  in  the  United  Kingdom — indeed,  some  species  over  all  the  earth  ; 
and  not  a  few  invade  window  plants,  conservatories,  greenhouses,  stoves, 
and  fruit  houses,  most  having  their  own  peculiar  food  plants.  They  are 
usually  called  green,  brown  or  black  “  flies,”  according  to  their  colour. 
All  are  much  alike  in  form,  soft  bodied,  fat  or  plump,  shining,  wingless  or 
winged.  The  wingless  are  found  in  the  asexual  (so-called)  generations, 
being  parthenogenetic,  the  word  parthenogenesis  (Greek,  parthenos,  a 
virgin  ,  genesis,  birth)  being  Professor  Owen’s  term,  applied  to  express 
those  cases  in  which  new  individuals  are  produced  from  the  ova  or  eggs 
of  females  without  contact  with  the  male.  The  term  is  also  occasion¬ 
ally  employed,  but  incorrectly,  to  denote  an  asexual  mode  of  reproduc¬ 
tion,  such  as  those  exemplified  by  Infusoria,  &c. — namely,  gemmation 
or  “  budding,”  and  fission,  or  simple  division  of  the  body  substance. 
In  the  autumn  aphides  deposit  eggs  in  the  axils  of  the  leaves  of  ever¬ 
greens  and  on  the  twigs,  generally  at  the  base  of  the  buds,  of  deciduous 
trees,  and  on  the  leaves  (under  side)  and  on  crowns  of  herbaceous  plants, 
always  near  the  point  of  new  growth  and  invariably  on  the  particular 
trees,  shrubs,  or  plants  affording  the  peculiar  and  essential  food  of  the 
species.  These  ova  live  throughout  the  winter  season  without  exhibiting 
any  apparent  progress  or  development.  They  are  developed,  however, 
in  the  following  spring,  and  the  eggs  invariably  produce  female  aphides 
only.  These  are  windless,  virgin  females,  which,  in  a  viviparous  manner 
and  without  the  presence  of  any.  male,  produce  a  second  generation 
resembling  themselves  in  the  wingless  state.  This  may  continue  through 
each  successive  generation,  through  nine  (as  observed  by  Bonnet)  or  eleven 
(as  traced  by  Duvau),  Kyber  having  observed  the  process  over  a  period 
of  four  years  without  being  able  to  detect  the  presence  of  a  single  male 
insect. 
During  the  summer  winged  females  may  appear  for  purposes  of 
migration,  but  it  is  not  until  the  approach  of  autumn  that  loinged  males 
make  their  appearance  in  the  final  generation  or  brood  of  the  “  fruitful 
virgins.”  These  males  pair  with  females  also  produced  in  the  brood, 
and  fertile  eggs  are  thus  produced,  which  lie  dormant  through  the 
winter,  and  repeat  in  the  succeeding  spring  the  reproductive  history  of 
their  predecessors.  In  a  single  year  as  many  as  twenty  generations  may 
be  produced,  and,  according  to  Eeaumur,  in  five  generations  the  vivi¬ 
parous  mode  of  reproduction  may  give  origin  to  5,904,900,000  forms,  as 
the  descendants  of  one  true  egg  or  aphis. 
What  a  momentous  matter  it  therefore  becomes  to  destroy  aphides  in 
the  summer  !  The  time  to  act  in  the  best  manner  as  regard  current  year’s 
infection  on  behoof  of  crops  is  in  the  early  springtime,  spraying  with 
some  approved  insecticide  when  the  buds  commence  swelling,  and  again 
before  the  blossoms  unfold.  If  another  spraying  be  given  as  soon  as  the 
fruit  is  set  there  would  be  few  aphides  but  what  migrated,  and  that 
must  be  on  the  wing. 
It  is  very  interesting  and  instructive  to  watch  the  migration  of 
aphides,  as,  for  instance,  the  “collier,”  “dolphin,”  or  Bean  aphis 
(A.  rnmicis).  This,  in  the  spring  time,  is  found  on  White  Campion 
(Lychnis  vespertina),  later  on  Docks  (Rumex  pulcher  and  R,  san¬ 
guineus,  chiefly),  early  in  June  on  Knapweed  (Centaurea  nigra),  and  by 
the  end  of  the  month  on  the  common  Thistle  (Carduus  arvensis), 
and  simultaneously  on  the  Bean  (Faba  vulgaris),  always  on  the 
flowering  stems,  and  in  every  instance  winged  females  appear  on  the 
various  host  plants  and  take  their  flight  from  one  to  the  other,  and  on 
plants  of  four  different  natural  orders  —  namely,  Caryophyllaceaa, 
Polygonaceaj,  Compositas,  and  Leguminosaa. 
Whenever  the  Bean  aphis  has  opportunity  it  leaves  every  other  plant 
for  the  Beans,  sometimes  having  buta  little  way  to  travel,  but  at  others  the 
listance  is  considerable,  being  frequently  a  matter  of  miles,  and  many 
halts  take  place  on  the  way,  always  with  an  augmentation  of  numbers, 
so  that  by  the  time  a  Bean  fleld  is  reached  Jane  is  in  and  they  swarm 
all  over  it,  multiplying  amazingly,  so  that  the  stems  and  blossoms  are 
smothered  almost  by  the  early  pare  of  July. 
When  the  Beans  or  Thistles  cease  growing  for  the  season,  the  winged 
aphides,  not  necessarily  last  brood,  talte  their  flight  to  herbaceous  plants, 
and  there  produce  the  autumn  or  late  summer  generation,  winged  males 
appearing  for  the  first  time  in  the  cycle,  and  the  females  deposit  the 
fertilised  ova  or  eggs  and  die.  In  some  cases  “  virgins  ”  may  survive 
the  winter,  but  this,  so  far  as  I  have  observed,  only  occurs  under  glass,  as 
with  the  green  aphis  on  various  plants  and  brown  aphis  on  Peach  shoots. 
These  are  viviparous,  but  in  the  great  field  of  Nature  the  late  summer 
brood  are  oviparous  females,  mostly  winged,  notalways,  but  always  winged 
males. 
Why  winged  viviparous  females  appear  in  early  summer  onwards  is 
ostensibly  and  feasibly  to  fly  off  to  “  fresh  fields  and  pastures  new 
but  there  is  a  far  more  pressing  reason — namely,  the  “  struggle  for 
existence,”  and  that  consists  in  throwing  the  enemy  off  the  scent.  The 
ladybirds  and  the  hawk  flies,  with  ichneumon  flies,  make  such  havo3 
amongst  the  aphis  hosts  by  their  larvae  that  without  the  special  provi- 
sion  of  wings  by  the  viviparous  females  on  occasion  their  tormentors 
would  eat  them  all  up.  Therefore,  ladycows  are  seen  in  swarms  after 
the  Hop  aphis  (A.  or  Phorodon  humuli)  has  migrated  from  the  Hop 
ground  to  the  Ballace,  Damson,  and  Sloe  trees,  aimlessly  striving  to 
find  their  prey,  which  so  adroitly,  and  for  purposes  of  self-preservation, 
has  given  them  the  “slip  then  their  turn  comes  for  destruction,  only 
those  surviving  that  can  get  a  good  feed  on  fruit  before  they  hibernate 
for  the  winter. 
Most  aphides,  in  nature,  have  two  food  plants — the  winter  and 
spring,  or  early  and  late  summer,  while  a  few  pass  the  winter  at  the 
roots  of  plants,  and  are  regularly  “  milched  ”  by  ants  ;  but  so  far  are 
the  aphides  from  appreciating  such  attentions  that  they  develop  wings 
in  every  generation,  so  eager  are  they  to  escape  from  the  abject  servi¬ 
tude  to  which  they  arc  subjected  by  the  ants.  When  aphides  are 
“  milched  ”  by  ants  the  power  for  increase  is  correspondingly 
diminished  ;  but  their  attentions  favour  migration,  as  also  do  the  perse¬ 
cutions  of  their  carnivorous  associates  ;  hence,  there  is  wholesale  attack 
on  crops  at  certain  times,  sometimes  on  one,  at  others  on  another,  but 
in  all  cases  by  the  species  peculiar  to  the  host  plant.  Thus,  the  Turnip 
aphis  (A.  rapse)  passes  the  winter  either  in  the  oviparous  state  (true 
egg)  on  the  leaves,  or  in  the  viviparous  condition  at  the  roots  of  plants 
of  the  natural  order  Caryophyllaceae,  commonly  Lychnis  species,  and  in 
their  migrations  to  Turnip  fields  despise  not  Hard-heads  or  Knapweed 
flower  stems.  So  it  is  with  most  species — they  come  from  the  wood¬ 
lands,  waste  places,  hedgerows,,- rubbishy  gardens  and  orchards,  and  the 
cultivator  suffers  correspondingly. 
In  the  spring  and  summer  time  the  attacks  are  most  confirmed  on 
trees,  including  fruit  trees  and  shrubs  ;  but  the  aphides  are  all  gone  by  a 
certain  time,  for  they  have  taken  to  themselves  wings,  and  that  is  while 
the  generations  of  ladybird  and  hawk-fly  larvEe  are  powerless  in  pupae. 
The  Apple  fly  (A.  mali)  clears  off  by  midsummer,  the  Gooseberry  fly 
(A.  ribis)  departs  earlier  ;  while  the  Currant  flv  (A.  rosas,  A.  rosarum, 
and  A.  dirhoda)  stay  until  July,  Plum  fly  (A.  pruni)  being  the  last  to 
depart,  though  not  long  preceded  by  the  Cherry  fly  (A  ce^a■^i) 
All  go  somewhere  for  a  time.  There  are  some  that  linger  on  soft 
growths  till  late,  and  these,  as  a  rule,  do  not  become  oviparous,  bub 
remain,  if  the  winter  is  favourable,  viviparous.  Some,  however,  usually 
migrate  as  winged  viviparous  females,  and  pass  the  winter  on  plants 
of  an  entirely  different  order  ;  for  the  dictum  that  aphis  species  confine 
their  attentions  exclusively  to  particular  plants  must  be  taken  with 
considerable  latitude  for  emergencies.  The  aphides  eventually,  however, 
never  make  any  mistake,  for  Apple  aphis  ova  are  always  deposited  on 
Apple  twigs.  Gooseberry  on  Gooseberry,  Currant  on  Currant,  Plum  on 
Plum,  and  so  on  with  the  species  living  on  herbaceous  plants. 
The  thing,  therefore,  is  to  prevent  such  migration  and  transference. 
This  can  be  done  very  effectively  in  the  case  of  Gooseberries,  Currants, 
and  Plums  by  cutting  off  the  points  of  the  shoots  beneath  the  leaves  of 
which  the  aphides  are  ensconced  and  burning  them.  The  pruning  will 
not  do  the  bushes  or  trees  the  least  harm  but  all  the  benefit  possible 
by  removing  the  cause  of  much  filth,  which  spoils  the  fruit  and  prevents 
the  leaves  that  elaborate  the  juices  from  performing  their  functions 
properly,  while  light  and  air  is  admitted,  of  considerable  advantage  to 
the  current  crop  and  formation  of  stout  buds  for  the  season  ensuing. 
Even  Black  Currants  are  not  ruined  by  the  topping  process,  for  if  done 
early  enough  (and  it  must  be,  if  to  profit  the  crop,  before  the  fruit  is 
clogged  with  sticky  fluid),  otherwise  flower  buds  will  remain  “  wood  ” 
or  these  will  be  formed  by  the  side  of  the  blossom  buds.  In  such  case 
there  will  not  be  any  migration  and  no  return  of  the  aphides  for  egg 
deposition. 
When  the  procedure  foreshadowed  has  been  neglected  and  the 
aphides  are  gone  there  is  no  reason  why  the  bushes  or  trees  should  not 
be  sprayed  in  late  summer  with  a  solution  of  soluble  petroleum,  especially 
bush  fruits,  also  Apple  and  Pear  and  Plum  trees  from  which  the  fruit 
has  been  gathered.  This  will  destroy  would-be  hibernating  red  spider 
and  make  the  bushes  or  trees  very  uninviting  for  aphides  depositing 
their  eggs. 
The  “  spiders  ”  do  not  deposit  eggs  (sacs)  in  autumn,  but  coil  them- 
