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1. Mosquito Investigation.
10
Enclosure in No. 14.
INVESTIGATIONS.
In view of the opening of the Panama Canal and the possible importation of yellow fever, the Secretary of State, by a letter of 22nd August, 1913, ordered that arrangements be made "to supply the Imperial Bureau of Entomology as soon as practicable with all information available as to the distribution of mosquitoes, and. in particular, of Stegomyia, in Hong Kong, and also for collections of mosquitoes to be sent to the Director of the Imperial Bureau."
The carrying out of this work was entrusted to me by the Principal Civil Medical Officer, and, though not yet completed, some definite results can now be recorded.
The total number of different samples of larvæ collected for breeding-out pur- poses now amounts to 14,909; from these over 41,000 adult mosquitoes have been bred out and pinned.
Approximately 26,000 of these species, derived from over 6,000 different samples of larvae, have been finally dealt with. The Imperial Bureau of Entomology has made the diagnosis in 21,000 of these specimens, the remaining 5,000 being dealt with locally. 15,000 specimens still remain to be classified, but it is expected that the majority of these can be classified here, only specimens of special interest being forwarded to the Imperial Bureau.
The following is a complete list of species so far found in Hong Kong. In every case the diagnosis has either been made or confirmed by the Imperial Bureau of Entomology :--
Anopheles indiensis, Theo.
Anopheles joyporiensis, Theo.
*Anopheles maculatus, Theo.
Anopheles karwari, James.
Anopheles maculatus, Theo., var.
*Anopheles minimus, Theo.
Anopheles minimus, Theo., var.
Anopheles rossi, Theo., var. indefinatus, Ludl.
*Anopheles sinensis, Theo.
Anopheles tesselatus, Theo.
Stegomyia fasciata.
*Stegomyia scutellaris, Walk.
Stegomyia W. alba, Theo.
*Armigeres obturbans, Walk.
Culex bitaniorhynchus, Giles.
Culex bitaniorhynchus, var. domesticus, Leic.
*Culex concolor, Ř.D.
*Culex fatigans, Wied.
Culez fuscocephalus, Theo.
Culex mimeticus. Noé.
Culex sinensis, Theo.
Culex sitiens, Wied.
*Culex tritaniorhynchus, Giles.
Culex virgapites, Edw., sp. nov.
Culex vishnui, Theo.
Culiciomyia pallidothorax, Theo.
Ficalbia minima, Theo.
Lophoceratomyia minutissima, Theo.
Lophoceratomyia rubithoracis, Leic.
Mansonioides uniformis, Theo.
Microdes malayi, Leic
Ochlerotatus macfarlanei, Edw., sp. nov.
Ochlerotatus greeni, Theo.
Ochlerotatus togoi, Theo.
Uranotania macfarlanei, Edw., sp. nov.
Dr. J. C. Thomson, in a 'Report regarding the mosquitoes that occur in the Colony of Hong Kong," 1902, records the only systematic mosquito work done in Hong Kong prior to the present investigation.
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As the result of a year's careful work he reports three anophelines (A. macu- latus, Theo., A. sinensis, Theo., A. minimus, Theo.) and seven named culicines, namely, C. fatigans, C. annulus, C. sericeus, C. reesii, C. concolor, Armigeres obtur- bans, and Stegomyia scutellaris.
I understand that Mr. Edwards, of the British Museum, regards C. annulus as a synonym of C. tritanorhynchus, and C. sericeus, Theo., and C. reesii, Theo, to he synonyms of C. fatigans.
Eight named species, therefore, remain from Dr. Thomson's report, and these have all been refound and are marked (with an asterisk) in the above list.
All the other species are new to Hong Kong, and the species Ochlerotatus mac- farlanei, Edw., Urānotœnia macfarlanei, Edw., and Culex virgapites, Edw. (male type) are entirely new.
A report dealing with the distribution, relative numbers, etc.. of all these species will be prepared when the whole collection has been worked through.
The Director of the Imperial Bureau has been good enough to return a complete set of all the above species, determined by Mr. Edwards of the British Museum. These are preserved in this Institute and are available for study.
The genus Stegomyia.-Three species of this genus are now known to exist in Hong Kong.
Stegomyia W. alba. This species is apparently rare, as it has only been found twice, being bred from larvæ taken from a hillside.
Stegomyia scutellaris.—This is probably the commonest mosquito in Hong Kong, and is well known to everyone. During the summer it is found in practically every Chinese house, breeding in small collections of water in old pots, tins, etc., and it is also found apart from houses on hillsides, etc. Whether the water in which it breeds is clean or dirty does not appear to matter.
Stegomyia fasciata. The search for this species has given considerable trouble, but the most recent results show that it not only exists here, but that it is much more prevalent than might be thought.
Stegomyia fasciata in Kowloon.-Ninety-six separate finds of Stegomyia fas- ciata larvae were made in Kowloon between the 15th April and the 29th September,
1914.
Appendix 1* gives the exact distribution of these larvæ, and the number of adults bred out and pinned from each sample.
A plan of Kowloon (plan 1†) is also attached, which shows their general distri- bution. From this plan it will be seen that the chief districts of Kowloon, namely, Yaumati, Mongkoktsui, Taikoktsui, and Hunghom, are all infected with Stegomyia fasciata. The European half of Kowloon point has not been examined.
The exact kind of receptacle in which the Stegomyia fasciata larvæ were found has not always been recorded by the various collectors, but, if the sixty-four kinds of Stegomyia fasciata larvæ made by me when collecting personally in the period 19th August to 23rd September be taken, the results may be tabulated as follows:-
Drinking Water Storage Receptacler.
Other Receptacle.
Earthenware
(Kong),
Wooden Buckut,
Wooden
Iron Bucket. Irou Tank.
Barrel.
Not Recorded.
25
11
i
3
1
18
10
1
Total 58
10
1
In fifty-three cases, therefore, or 84 per cent. of the total finds, the larvæ were obtained in the stored clean water used for drinking, cooking, etc.
In the remaining eleven cases the finds were made three times in miscellaneous jars in yard, twice in flower pots, once in a wooden tank for soaking bamboos in (chairmakers), three times in jars in preserved fruit factories, once in a jar in a woodyard, and in one case no record of the jar was made.
In all cases the finds were made in densely built-over areas, either in the houses themselves or in their immediate vicinity.
* Not printed.
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