A.  maculipennis  is  the  most  important  species  of  the  three,  as  it  is
common  and  frequents  the  neighbourhood  of  houses.  It  begins  to
deposit  its  eggs  in  the  spring  in  weed-grown  ditches  and  ponds  in  the
neighbourhood  of  houses.  A  point  to  be  noted  is  that  this  species  is
normally  tided  over  the  winter  season  not,  as  is  usual,  in  the  larval
condition  but  in  the  adult  stage — fertilized  females  hibernating  in  warm
cowsheds,  stables  or  other  outhouses  where  they  may  readily  be  found
hanging  on  to  the  roof.  These  hibernating  females  are  not  entirely
inactive  for  they  take  advantage  of  occasional  warm  sunny  days  to  get
a  meal  of  blood.  It  is  obvious  from  what  has  been  said  that  the  numbers
of  A .  maculipennis  in  such  a  cold  temperate  climate  as  that  of  Britain  are
controllable  (i)  by  the  destruction  of  the  hibernating  females  by  fumi-
gation or  whitewashing  and  (2)  by  removing  the  vegetation  from  ditches
and  ponds  near  houses.
A.  bifurcatus,  whose  larvae  frequent  the  mud  at  the  bottom  of  ditches
and  winter  in  that  condition,  and  A.  plumbeus,  whose  larvae  have
been  found  usually  in  holes  in  trees,  are  more  elusive  as  regards  con-
trol measures  but  they  are  of  much  less  practical  importance  than
A.  maculipennis.
No  special  attention  has  been  drawn  so  far  to  the  obvious  advisability


ZOOLOGY  FOR  MEDICAL  STUDENTS  CHAP.
