would  hold  good  for  many  portions  of  the  country,  and  it  may  safely 
be  said  that  on  the  plateau  the  vegetation  and  temperature  approach 
the  temperate  more  closely  than  the  tropical  type.  At  the  level  of  the 
lakes  and  in  the  large  river  valleys,  the  conditions,  of  course,  are 
niuch  different,  and  are  sufficiently  well  marked  to  be  quite  perceptible 
in  passing  from  the  low  to  the  high  levels. 
There  are  other  factors,  than  the  altitude  and  temperature,  which 
would  tend  to  limit  the  presence  of  Gl.  palpalis  in  the  main  portion 
of  the  territory  with  which  we  are  dealing.  The  annual  rainfall,  for 
instance,  is  comparatively  low,  from  40  to  50  inches,  and  the  drainage 
is  so  complete  that,  except  in  the  rains  (end  of  October  to  end  of 
March),  all  but  the  main  rivers  are  dried  up,  so  that  the  air  lacks  the 
humidity  which  is  apparently  necessary  for  the  development  of  this 
species.  The  lack  of  shade  is  another  factor.  The  whole  of  the 
country  is  covered  with  a  very  thin  type  of  bush  formed  by  small, 
scraggy  trees  which  afford  very  little  shade.  At  frequent  intervals 
the  bush  is  interrupted  by  grassy  ’’  dambos  ’  or  plains,  of  varying  size, 
which,  in  the  rains,  act  as  reservoirs  into  which  the  water  drains  from 
the  surrounding  localities  and  from  which  the  streams  take  origin. 
The  shores  of  Lake  Tanganyika  are  anomalous,  in  that  the  fly  is 
found  where  there  is  practically  no  shade,  but  the  greater  humidity 
and  higher  temperature  are  doubtless  important  factors  in  determining 
their  presence  there. 
Most  of  the  streams  in  Rhodesia  and  Nyasaland  have  been 
insufficiently  explored  for  Gl.  palpalis,  and  while  it  has  not  as  yet 
been  found  on  many  of  them,  it  would  be  advisable  that  more  time 
should  be  devoted  to  the  search  before  an  absolutely  negative  result 
is  recorded.  So  far  as  the  general  conditions  go,  there  is  no  reason 
to  suppose  that  the  species  would  not  flourish  just  as  well  on  many  of 
the  more  central  streams  as  they  do,  for  example,  on  parts  of  the 
Luapula. 
III.  DISTRIBUTION  OF  TSETSE  FLIES 
I.  Glossina  palpalis. 
A.  In  North-Eastern  Rhodesia. 
In  our  earlier  report,  we  said  that  this  fly  had  been  found  on  both 
banks  of  the  Luapula  river  from  Kapwepwi’s  (il°3o'  S.)  to  Kasiwa’s, 
a  village  on  the  British  side  about  io°l5'  S.  Beyond  Kasiwa’s, 
