H. L. Duke 363 
(6) Entebbe shore. Sept.-Nov. 1903. No natives. No antelope. (First R.S. Commission.) 
Total flies fed ... 
... 1421 
Number of infections ... 
... 1 
Percentage of infective flies 
... 0-07. 
(C) 
Entebbe shore. June-Sept. 1904. No natives. 
No antelope, 
Total flies fed ... 
... 2299 
Number of infections ... 
... 0 
Percentage of infective flies 
... 000. 
(d) Mainland. 
Nov. 1909-July 1910. (Bruce’s Commission.) 
Total flies fed ... 
... 28274 
Number of infections ... 
... 18 
Percentage of infective flies 
... 006. 
(«) 
Mainland. 
Aug. 1910-Feb. 1911. (Fraser and Duke.) 
Total flies fed ... 
... 51078 
Number of infections ... 
... 5 
Percentage of infective flies 
... 009. 
(/) Mainland. 
Jan. 1920-Jan. 1921. 
Total flies fed ... 
... 6441 
Number of infections ... 
... 2 
Percentage of infective flies 
... 003. 
(g) Damba Island. Jan.-June, 1910. (Bruce’s Commission.) 
Total flies fed ... ... ... 6356 
Number of infections ... ... 2 
Percentage of infective Hies ... 0-03. 
(h) Damba Island. May, 1911. (Carpenter.) 
Total flies fed ... ... ... 885 
Number of infections ... ... 1 
Percentage of infective flies ... 0*11. 
( i ) Damba Island. Sept.-Dec. 1920. 
Total flies fed ... ... ... 3732 
Number of infections ... ... 3 
Percentage of infected flies ... 0-08 
( j ) Sesse Islands: Bugalla and Kome. Late 1911 and early 1912. (Carpenter.) 
Total flies fed ... ... ... 1.2000 
Number of infections ... ... 2 
Percentage of infective flies ... 0-06. 
(k) Sesse Islands: Nsadzi and Kimmi, before arrival of antelope. 1910-1911. (Fraser and 
Duke.) 
Total flies fed ... ... ... 14209 
Number of infections ... ... 0 
Percentage of infective flies ... 0-00. 
( l) Sesse Islands: Nsadzi and Kimmi, after arrival of antelope. May-July, 1914. (Carpenter.) 
Total number of flies fed ... 2076 
Number of infections ... ... 1 
Percentage of infective flies ... 0*04. 
The highest infectivity rate in these experiments is that obtained when a 
heavily infected native population was living in the fly zone at Entebbe in 
190.3, but in these experiments, as only flies which obviously contained blood 
were counted as having fed, it is probable that the percentages are too high. 
Since that time the infectivity level has remained remarkably constant. On 
