738
REPORT REGARDING THE MOSQUITOES THAT OCCUR IN THE COLONY OF HONGKONG.
HONGKONG, 15th February, 1902.
SIR-I have the honour to submit, for purposes of the Annual Medical Report, the results of a systematic examination and classification of the mosquitoes that prevail in Hongkong and its Depend- encies, on which I was engaged during the twelve months ending 30th September, 1901.
For somə months previous to September, 1900, I was working at the subject as I had opportunity, but my field of observation was limited to the Colony itself until in that month the Honourable F. H. MAY, C.M.G., Captain Superintendent of Police, kindly consented to my proposal that I should be supplied with at least one dozen mosquitoes from each of the Police Stations throughout Hongkong itself and the New Territory once a week for a year. As the Police Stations are approximately equally scattered over the whole area, the mosquitoes that were sent to me may be assumed to fairly satisfactorily represent the actual relative prevalence of these insects in this locality..
2. I distributed a number of glass test-tubes to each of the thirty-six Police Stations, with general instructions for the catching and transmitting of the insects in such a way as to avoid injury to them. They were to be caught by means of the glass tubes, killed by a whiff of tobacco-smoke, and sent enclosed in match-boxes to the Central Police Station, from which they would be duly forwarded to me. It was requested that about two-thirds of each consignment should be caught in the evening, or from mosquito-curtains in the early morning, and the remainder from species seen flying about in the day time; and further that no selection of any kind should be made, the first dozen or so caught on any given date being sent.
The arrangements made have been carefully carried out by the officers in charge of the stations, with few exceptions; and I beg to express my thanks to the Captain Superintendent of Police, Chief- Inspector MACKIE, and the officers of the Police Force for their hearty co-operation in this research.
3. During the twelve months, 1st October, 1900, to 30th September, 1901, 32,266 insects were sent to me from the Police Stations. Of these, 31,390 proved to be mosquitoes; the others were chiefly insects belonging to cognate families, such as fungus gnats (Mycetophilida), midges (Chironomide), sand flies (Simulidae), &c.
1,169, .., 3.7 per cent. were Anopheles, of three species, and 30,221, i.e., 96.3 per cent. were Culex, of twelve species. As is shown in Appendix II, the number of species of Culex is probably considerably larger, some that I describe as varieties being perhaps distinct species.
4. I enclose a Table (Appendix I) showing in detail my observations during the year as regards the various Police Stations. I show for each station the number of specimens received, the number of Anopheles and Culex respectively, and the names of the species of both that have come from the station. I describe the different species by letters corresponding to those used in the Systematic Account of Hongkong Mosquitoes given below (Appendix II). Similar tables showing the same facts, but without the names of species, for each month and each quarter of the year are included in my quarterly reports on this subject, which have appeared in the Government Gazette.
5. The monthly percentage of Anopheles and Culex has been as follows:--
Anopheles.
Culex.
Mosquitoes examined.
Number.
Per cent.
Number.
Per cent.
October,
401
106
26.4
295
73.6
November,
796
50
6.3
746
93.7
December,
2,342
138
5.9
2,204
94.1
January,
3,380
143
4.2
3,237
95.8
February,.
2,524
35
1.4
2,489
98.6
March,
1,586
49
3.1
1,537
96.9
April,
3,501
115
3.3
3,386
96.7
.May,
5,476
116
2.1
5,360
97.9
June,
3,562
111
3.1
3,451
96.9
July,
2,582
138
5.3
2,444
94.7
August,
2,296
88
3.8
2.208
96.2
September,
2,944
80
2.7
2,864
97.3
Last Quarter, 1900,
3,539
294
8.3
3,245
91.7
First Quarter, 1901,
7,490
227
3.
7,263
97.
Second Quarter, 1901,
12,539
342
2.7
12.197
97.3
Third Quarter, 1901,
7,822
306
3.9
7.516
96.1
The Twelve Months,
31.390
1,169
3.7
30,221
96.3.