205 



which, for a day or two after heavy rains, ascended tributary 

 streams for short distances and were found isolated in the upper 

 reaches of these. In one main street-drain fish are found 

 towards the sea-end even in the dry season, and these are 

 transferred as required to other drains, private wells, etc. Private 

 individuals are having their wells stocked with fish and this has been 

 found to be a better prophylatic measure against the breeding of 

 mosquitos than well-covers. Fish from the sea introduced into 

 comparatively fresh water, take some time in adapting themselves to 

 it, but re\ave after a day or two and destroy larvae with avidity. The 

 following figures are given with regard to one particular drain which 

 had been dry for some time and filled up to 90 yards from the sluice 

 gate during high tide in April, the average depth being 4 inches. On 

 23rd April, the larvae present, half-grown or larger, were estimated to 

 number 2,100. Eleven fish, six of 4 inch length and five of 2 inch, 

 which had been kept for some time in a tub of fresh water, were intro- 

 duced at 11 a.m. on this date and at 9 a.m. the following morning not 

 a single larva could be found. Three fish about IJ inches long were 

 put into a bath of well water on the 29th October and on the 30th 

 full-grown larvae were introduced at intervals of about 5 minutes as 

 follows : 12, 13, 25, 30, 30. In 20 minutes, all these larvae with the 

 exception of seven had been eaten and 2 hours later all had disappeared. 

 On 31st October two of these fish consumed thirty larvae in 3 minutes. 

 Details of numerous experiments are also given, all tending to show 

 that if the fish are properly treated, their capacity for destroying 

 mosquito larvae is very great. 



Reports of the Sleeping Sickness Mission in Principe, December 1913 to 

 March 1914 (8 pp.) and April to June 1914 (6 pp.) embodied in 

 Reports of Consul General Hall to Sir Edward Grey. [Received 5th 

 September 1914 and 21st October 1914.] 



These reports are a continuation of those for October and November 

 1913 [see this Review, Ser. B, ii, pp. 121-124]. In November and 

 December 1912, more than 22,000 flies were caught in each month, 

 and one year later the catch dropped to 1,358 in November and only 

 134 in December, although a larger number of labourers was employed 

 in the work. On the banks of the River Papagaio, formerly very 

 much frequented by flies, none were caught in the first fortnight of 

 December 1914, and in another fly resort the same number of labourers 

 caught only 25. Other places formerly of evil repute were also visited 

 and in one no flies were found and in another only three. 



During the month of December a very large estate, worked by an 

 Agricultural Company, estimated to comprise about half the area 

 of the island and formerly for many years a principal centre of fly 

 and sleeping sickness, was dihgently searched by 45 men and no fly 

 was found. The nature of the country and the excellent conditions 

 for the breeding of Glossina are described. In 1908, 23'9 per cent, of 

 the employees on this estate were infected. In 1913, the figure had 

 fallen to 11*1, and in January 1914, to 8. Summarising the results 

 up to the end of January 1914, 170 men, employed daily, captured 



