26i 
II.  CONDITIONS  UNDER  WHICH  WORK  WAS  DONE 
Our  observations,  in  the  case  of  Glossina  falpalis  (var. 
wdlniani),  were  carried  out  on  Matondwi  Island  at  the  southern 
extremity  of  Lake  Tanganyika.  This  island  lies  between  two  and 
three  miles  from  the  mainland,  and  measures  about  one  mile  in  length 
by  half  a  mile  in  width.  It  slopes  with  more  or  less  abruptness  from 
the  water  to  a  height  of  about  one  hundred  feet,  and  is  composed  of 
rough  broken  stones  on  which  grows  a  thin  scrubby  type  of  bush. 
The  shores  are  similar  to  those  of  the  lake  in  that  they  present  at 
some  places  dense  growths  of  reeds,  at  others  scattered  mimosa  trees, 
and  at  others  bare  rocky  stretches  devoid  of  vegetation.  Glossina 
fal falls  was  very  abundant  along  the  shore,  and  large  numbers  were 
caught  daily  without  any  difficulty. 
For  more  than  the  past  twenty  years  the  island  has  been 
uninhabited,  and  during  this  period  has  practically  never  been  visited 
even  temporarily  by  the  natives  of  the  mainland.  The  fauna  is 
composed  of  some  crocodiles,  large  numbers  of  birds,  principally  water- 
species  (e.g.,  darters,  egrets,  herons,  &c.),  a  few  snakes,  and  a  species 
of  mouse ;  no  other  mammalia  exist,  save  perhaps  an  occasional 
visiting  hippopotamus. 
During  the  month  of  July,  1908  (middle  of  dry  season)  we  spent 
four  weeks  on  Matondwi,  and  in  November,  1908  (just  after  the  rains 
had  commenced),  returned  for  a  three  days’  visit. 
The  work  with  Glossina  morsiians  was  done  at  a  camp  near 
Kambole,  about  50  miles  west  of  Abercorn,  during  the  month  of 
October,  1908  (end  of  dry  season).  In  this  immediate  neighbourhood, 
game  is  very  scarce  at  that  time  of  the  year.  Only  an  occasional 
duiker  was  seen  while  we  were  at  this  place. 
III.  METHODS 
We  found  the  best  method  of  extracting  the  intestine  was  as 
follows. 
The  fly  was  laid,  dorsal  surface  downwards,  on  a  clean  slide,  so  that 
the  last  segment  nearly  touched  a  large  drop  of  salt-citrate  solution 
(NaCl  and  Sodium  Citrate  a  a  O' 5  per  cent.)  in  the  centre  of  the  glass. 
A  mounted  needle  was  then  pressed  against  the  posterior  surface  of 
