236 



Report on special Investigations carried out in the Bacteriological 

 Institute and in the Public Mortuary, Victoria, during the six 

 months, January 1st to June 30th, 1913. — Hon<i Kong, 4 pp. 

 Keceivod l)y Ihe Colonial Office 29th Sept. 1013. 



All investigation of the iiiosqiiitos of Hong Kong' was com- 

 menced in July 1912 with the view (1) to search for the presence 

 or absence of Stefjomyia fasciata; (2) to collect Anopheline mos- 

 quitos, with special reference to their exact distribution in the 

 Colony, and in order to discover which of the species are malaria- 

 carriers ; and (3) to obtain a g-eneral collection of Culicines. 



The Steqomyia survey of the city of Victoria covered a period 

 from 1st July 1912 to' 30th June' 1913 and 17,361 house-visits 

 were made, that is to say about 2 per house. The percentage of 

 houses in which larvae were found varied markedly with the 

 season of the year and the positive results obtained by Inspector 

 Watson were found to be considerably higher than those recorded 

 by the ordinary Sanitary Staff. The Inspector found larvae in 

 from 80 per cent, of the houses visited downwards to almost nil in 

 cold weather in February. On the other hand the Sanitary Staff 

 figure was never more than 10 per cent. The writer of the Eeport 

 does not consider the Inspector's figures as an over-estimate, and 

 says that, on the contrary, his results would have been consider- 

 ably higher but for the fact that he became so well known to the 

 Chinese that his appearance in the street was a signal for a 

 general emptying of pots, water-barrels, etc. Some 1,238 samples 

 of larvae were obtained from more than as many houses and 6,511 

 mosquitos were bred out and pinned. A larger number were 

 examined and as they were all of the same species were not pre- 

 served. The examination is not yet completed, but with one 

 exception, no Stegomyia fasciata were found. The predomi- 

 nating mosquito is Stegomyia scutellaris, which can be found 

 almost everywhere. Culex fatigans and other Culicines form a 

 small percentage. The area in which the single specimen of S. 

 fasciata was found was repeatedly searched, but no further speci- 

 mens had been obtained to date. If further experience confirms 

 the result of the work already done, a very curious position will 

 be displayed. Stegomyia fasciata is recorded by Theobald as 

 common in Japan,' the Philippines and Singapore. From all 

 these places ships are constantly coming to Hong Kong, and as 

 S. fasciata is said to be a good traveller on ships, it would appear 

 that it must frequently have been brought to the town. Dr. 

 Werkman, of Leyden, who has been working on mosquitos at the 

 Institute, had no difficulty in collecting and bringing back 

 specimens of S. fasciata from the ports of Tandjoing Priok, 

 Semarang and Soerabaya in Java, during a trip on the Dutch 

 steamship line which is constantly running between Hong Kong 

 and Java. There is no doubt that many ships have entered the 

 port of Hong Kong for many years past from ports infested with 

 S. fasciata, so that there has been ample opportunity for the 

 importation of the insect. Similarly Dr. Chan Tsun Kun, the 

 Government Bacteriologist at Canton, has informed the writer of 

 the Eeport that in spite of diligent search no S. fasciata have 

 been found in Canton. 



