.5«4 
Disused  ‘sakia"  or  water-wlieel  pits  are  permanent  breeding-places, 
but  when  the  water  level  in  them  is  raised  to  near  the  surface  of  the 
land  by  infiltration  from  the  Nile,  it  is  possible  that  the  species  ot 
mosquitoes  breeding  in  them  may  differ,  since  the  water  will  be  more 
exposed  to  light. 
Tn  addition  to  the  breeding  places  mentioned  above,  there  are  the 
cesspits,  which  supply  Cairo  with  an  unfailing  supply  of  Culex 
faiigaus,  Wied.,  throughout  the  year,  their  numbers  varying  with  the 
season  (temperature).  It  is  probable,  however,  that  many  old  or 
little-used  cesspits  and  wells,  which  at  other  times  of  the  yeai  aie 
dry,  become  converted  into  breeding-places  for  Culicids  during  the 
flood. 
In  the  case  of  gardens,  agricultural  land,  and  borrow-pits,  flooded  b)/ 
infiltration  from  the  riv'er,  one  finds  almost  inx'ariably  that  the  surface 
of  the  water  is  overgrown  with  grass,  water-plants  and  algae 
{Spirogyra,  sp.,  Hydrodiclyon,  sp.).  These  places  then  form  admirable 
breeding-sites  for  Anopheline  as  well  as  Culicine  larvae.  By  about 
the  middle  of  October,  igoS,  and  again  in  1909,  collections  of  water 
of  this  nature  were  swarming  with  Culicine  larvae  and  to  a  lesser 
degree  with  the  larvae  of  Cellia  pharoensis,  Theob. 
Such  was  the  state  of  affairs  on  the  Island  of  Ghezireh  in  October 
and  November,  1908-1909.  Ghezireh  is  situated  opposite  Cairo,  and 
is  connected  with  both  banks  of  the  river  by  bridges.  On  the  island 
there  is  a  large  resident  European  population  with  their  native  and 
European  servants ;  there  are,  in  addition,  a  considerable  number  of 
native  and  European  w^orkmen,  wflio  go  to  and  from  their  daily  work. 
Again  there  is  what  may  be  described  as  a  floating  riverside 
population  (chiefly  natives)  living  in  house-boats  (‘  dahabiehs  ’) 
moored  against  the  banks,  and  in  the  ordinary  Nile-boats  engaged  in 
the  transport  of  merchandise. 
As  many  parts  of  the  island  are  low^-lying  they  suffered 
considerably  from  flooding  by  infiltration  from  the  river.  Culex,  spp. 
bred  in  countless  numbers,  and  Cellia  pharoensis  in  ‘thousands.’ 
Grabhamia  willcocksii,  Theob.,  w’as  also  very  numerous.  The 
females  of  this  last  species  are  vicious  blood-suckers  as  well  as  plant 
feeders,  but  they  do  not  appear  to  enter  houses  in  any  number.s. 
Although  Cellia  pharoensis — a  supposed  malaria  carrier — was 
very  abundant  in  the  autumn  of  1908  in  Ghezireh,  yet,  so  far  as  the 
