4«3 
And  that  being  the  case,  it  is  equally  clear,  as  I  shall  show 
directly,  that  in  a  locality  where  Malaria  is  prevalent,  preventive 
measures  against  the  disease  must  be  directed  against  either  of  these 
factors,  or,  better  still,  against  both. 
VI.  THE  ANOPHELINE  MOSQUITO 
1  have  mentioned  that  Malaria  can  only  be  transmitted  by  means 
of  a  particular  species  of  mosquito,  the  Anophelines,  and  experiments 
carefully  carried  out  in  many  parts  of  the  world  with  the  object  of 
growing  the  malarial  parasites  in  other  varieties  of  mosquito  have 
invariably  been  unsuccessful,  so  that  we  may  take  it  as  proved  that 
the  Anopheline  is  the  only  means  by  which  Alalaria  is  transmitted. 
This  fact  naturally  is  of  very  great  assistance  in  our  campaign  against 
Malaria,  for  the  Anopheline  has  special  habits,  special  characteristics, 
and  selects  special  conditions  for  breeding  and  growth,  so  that  it  is 
advisable  that  we  should  be  familiar  with  these. 
The  life  history  of  an  Anopheles  Mosquito,  as  of  other  insects, 
consists  of  four  stages  :  — 
1.  First  of  all,  the  adult  female  lays  its  Eggs  in  water  or  near  it, 
and  in  warm  weather  these  hatch  out  in  a  day  or  two  to  form 
2.  The  Larvae,  short,  wriggling  bodies,  which  are  familiar  to 
everyone  as  occurring  in  standing  water.  They  are  provided  with 
breathing  apertures,  and  it  is  important  to  remember  that  they  must 
come  to  the  surface  to  breathe.  The  larvae  of  the  Anopheline  Mosquito 
may  be  recognised  by  the  fact  that,  when  in  repose,  they  lie  fat  under 
the  surface  of  the  water,  while  the  larvae  of  Culex  and  Stegomyia 
hang  head  downwards,  with  their  tails  and  breathing  tubes  on  the 
surface. 
3.,  After  about  a  week  the  Pupa  is  formed,  a  shorter  body  with  a 
large  head,  which  also  has  to  come  to  the  surface  to  breathe. 
4.  Finally,  in  two  or  three  days  the  pupa  develops  into  the  adult 
Anopheline.  The  latter,  when  at  rest,  can  generally  be  distinguished 
by  their  characteristic  attitude.  While  the  ordinary  mosquito  stands 
with  its  body  parallel  to  the  wall,  the  Anopheline  rests  with  its  body 
in  the  air,  and  its  head  and  trunk  as  if  boring  down  into  the  wall.  It 
is  important  to  note  also  that  the  habits  of  the  Anophelines  are  mainly 
nocturnal — it  comes  out  as  a  rule  at  dusk,  and  retires  at  sunrise.  It 
is  principally  dangerous,  therefore,  for  a  limited  number  of  hours. 
