226
22 a
11
As to the relative prevalence of the three species of Anopheles, I am not able to speak as regards the 294 Anopheles which I received during the last quarter of 1900, but of 875 received during the three quarters of 1901 included in this research, 483 were Anopheles Sinensis, 249 Anopheles Maculatus, and 143 Anopheles Minimus.
10. I have differentiated twelve species of Culex, which I describe at length in the Appendix. There are probably considerably more, as some of the varieties of certain species which I describe may be regarded by entomologists as distinct species. I do not attempt to follow Theobald in his new classification of mosquitoes, just published in the Tropical Journal, into twenty-four different genera, breaking up the old genus Culex into some twenty new genera, based on the arrangement of the scales which cover the insects. For instance, he now describes Culex Scutellaris and Culex Obturbans, two of the most common of the Hongkong mosquitoes, as Stegomyia Scutellaris and Armigeres Obturbans. Culex Fatigans, Culex Scutellaris, Culex Obturbans, and Culex Concolor have been described before. Culex Aulus, Culex Sericeus, and Culex Reesii are new species, and have been named by Mr. Theobald from specimens which I submitted to him. Culex Reesii he has so called from our mutual friend Dr. D. C. Rees, lately Superintendent of the London School of Tropical Medicine, who put me in communication with Mr. Theobald. The insects which I have indicated by the letters, "n", "o", "p", "r", "r", and "s", I have carefully described, but not named. "p" may be Culex Fuscanus; the others are, I think, new species but this question I shall remit to Mr. Theobald at the British Museum.
Culex Scutellaris is the black and white striped mosquito so common all over the Colony during the day time; Culex Fatigans and Culex Reesii are the equally common brown mosquitoes, to be found everywhere and at all seasons in the evening; Culex Obturbans is the very large dark mosquito, also very widely prevalent. The others are less abundant, but for the most part occur pretty generally throughout the Colony.
It may be noted in passing that Culex Fatigans is the most usual intermediate host of the blood parasite, Filaria Nocturna, the cause of Elephantiasis and its kindred diseases, by no means uncommon in this locality.
While Anopheles as a rule only use for breeding purposes clean water in more or less natural collections, the various species of Culex lay their eggs wherever stagnant water exists, in broken dishes, empty tins, flower pots, water tanks or barrels, drain traps, and the like. Nothing is too dirty to have its appropriate mosquito developing in it. Culex Obturbans is the most loathsome of all in its larval state, finding its most favourable conditions in decomposing urine.
11. I do not propose to enter here into details of prophylaxis against these insects, which I have dealt with in special reports: but direct attention to certain observations which I made during the winter.
I found the larvae of Anopheles in the nullahs throughout the whole winter, in scarcely diminished numbers, though there were few in the pupa stage, and development at that season is evidently very slow or arrested.
I was able to note the effects of severe cold at the beginning of February. On 1st February, I had made a careful examination of the Kennedy Town nullah, and found Anopheles larvæ plentiful. On the 3rd there was a sudden rapid drop in the temperature, and when I examined the stream again on the 5th there were few larvæ to be seen. It seemed as if they had been killed by the cold. But fortunately I had some larvæ under observation at the time in a glass jar in my verandah. Under the influence of the cold these became torpid or sluggish, and most of them seemed dead.
On the 7th, however, the sun shone out brightly, and the seemingly dead ones as well as the others became quite lively again. It is probable, therefore, that much of the diminution in numbers of the larvae in the ravines during the winter is more apparent than real, since they are most easily recognised in ordinary circumstances by their very characteristic movements when disturbed.
Dr. J. M. Atkinson,
Principal Civil Medical Officer,
&c.,
I have the honour to be,
Sir,
Your obedient Servant,
JOHN C. THOMSON, M.D., M.A.
APPENDIX I.
PREVALENCE OF MOSQUITOES, DURING THE YEAR ENDING 30 SEPTEMBER, 1901.
NAME OF STATION Specimens received. ANOPHELES. CULEX. Other Genera. Central Station, 1,360 6 1,334 Nil. No. 1 Station.. 576 1 574 No. 2 1,255 1,255 No. 3 1,177 1,177 No. 5 156 107 No. 6 71 +1 71 No. 7 107 7! No. 8 462 447 Kennedy Town, 63 62 15 764 716 48 Mt. Gough, 63 61 2 872 Pokfulam, #be 831 efhikomor 20 Aberdeen, 735 b 681 efghikmur 47 Stanley, 980 15 948 ube efhikuor Shek 0, 750 116 632 it efhimno Shaukiwan, 1,579 1,538 eflikmoor 607 Tsat Tsze Mui, 47 553 abe efhikn Tsim Sha Tsui, 678 676 elbiku Yaurati, 1,069 B 1,065 efghikars Tuk Tsun Heung, 572 & 557 Stone Cutters' Island, efhiknor 81 80 elkon Hung Hom,..... 729 725 Kowloon City, 1,726 a 1,716 ofhiknor Nil. Tai Po, 662 43 648 8 abc abo Sha Tau Kok,. Kat 0,.... 819 191 520 544 618 efghikuops efghikn 90 96 Sheung Shui, efhinnopr 4,428 414 3,987 efhiknopr 10 27 709 696 Sheung Shui, ofhi 13 $29 10 a b 906 efbikinor 14 916 14 abe 823 efhiknor 79 1,853 113 1,728 abe efhikinnor 12 251 12 A h 283 efghikn 6 408 38 361 a be ofhiko 9 238 78 * 148 efhikm 4,704 1 4,703 b Sai Kung, 628 30 574 a be efhikn efhiknor 24 Total... 32,266 1,169 30,221 abe efghik mnoprs 876 Less, 876 Net Total..... 31,390Sha Tin Gap,
Sha Tin,
San Tiu,
Au Tait, Ping Shan, Tai 0,-
Tung Chung, Cheung Chuu,. Lammia,
APPENDIX II.
AN ACCOUNT OF HONGKONG MOSQUITOES. A--Anopheles Sinensis (Wiedemann)." Sub-species; Annularis.
Wings spotted. Dark brown costa, with two lighter interruptions. Dark brown spots irregularly placed on wing field. Legs brown. White-banded at joints. White bands at apices of tarsi.
Antennæ and palpi brown. Proboscis darker brown. Thorax brown. Linear markings of a deeper brown. Abdomen brown, unbanded.
Length, 5 mm.
B-Anopheles Maculatus. A new species.
Wings spotted, transparent. Four linear black spots along costa, with three pale intervals. Also faint linear spots on wing field at points on course of veins.
Legs black, white-banded. White bands at apices of tarsi.
Antenna grey.
Palpi black, white-banded, and white-tipped. Proboscis dark-brown, with pale tip. Thorax brown, with grey-white tomentum.
Abdomen brown, unbanded.
Length, 4 mm.
226
22 a
11
As to the relative prevalence of the three species of Anopheles, I am not able to speak as regards the 294 Anopheles which I received during the last quarter of 1900, but of 875 received during the three quarters of 1901 included in this research, 483 were Anopheles Sinensis, 249 Anopheles Macu- latus, and 143 Anopheles Minimus.
10. I have differentiated twelve species of Culex, which I describe at length in the Appendix. There are probably considerable more, as some of the varieties of certain species which I describe may be regarded by entomologists as distinct species. I do not attempt to follow THEOBALD in his new classification of mosquitoes, just published in the Tropical Journal, into twenty-four different genera, breaking up the old genus Culex into some twenty new genera, based on the arrangement of the scales which cover the insects. For instance, he now decribes Culex Scutellaris and Culex Obturbans, two of the most common of the Hongkong mosquitoes, as Stegomyia Scutellaris and Armigeres Obturbans. Culex Fatigans, Culex Scutellaris, Culex Obturbans, and Culex Concolor have been described before. Culex Auulus, Culex Sericeus, and Culex Reesii are new species, and have been named by Mr. TuCOBALD from specimens which I submitted to him. Culex Reesii he has so called from our mutual friend Dr. D. C. REES, lately Superintendent of the London School of Tropical Medicine, who put me in communication with Mr. THEOBALD. The insects which I have indicated by the letters, "n", "o", "p", "r", "r", and "s", I have carefully described, but not named. "p" may be Culex Fuscanus; the others are, I think, new species but this question I shall remit to Mr. THEOBALD at the British Museum.
Culex Scutellaris is the black and white striped mosquito so common all over the Colony during the day time; Culex Fatigans and Culex Reesii are the equally common brown mosquitoes, to be found everywhere and at all seasons in the evening; Culex Obturbans is the very large dark mosquito, also very widely prevalent. The others are less abundant, but for the most part occur pretty generally throughout the Colony.
may
It be noted in passing that Culex Fatigans is the most usual intermediate host of the blood parasite, Filaria Nocturna, the cause of Elephantiasis and its kindred diseases, by no means uncommon in this locality.
While Anopheles as a rule only use for breeding purposes clean water in more or less natural collections, the various species of Culex lay their eggs wherever stagnant water exists, in broken dishes, empty tins, flower pots, water tanks or barrels, drain traps, and the like. Nothing is too dirty to have its appropriate mosquito developing in it. Culex Obturbans is the most loathsome of all in its larval state, finding its most favourable conditions in decomposing urine.
11. I do not propose to enter here into details of prophylaxis against these insects, which I have dealt with in special reports: but direct attention to certain observations which I made during the
winter.
I found the larvae of Anopheles in the nullahs throughout the whole winter, in scarcely diminished numbers, though there were few in the pupa stage, and development at that season is evidently very
slow or arrested.
I was able to note the effects of severe cold at the beginning of February. On 1st February, I had made a careful examination of the Kennedy Town nullah, and found Anopheles larvæ plentiful. Ou the 3rd there was a sudden rapid drop in the temperature, and when I examined the stream again on the 5th there were few larvæ to be seen. It seemed as if they had been killed by the cold. But for- tunately 1 had some larvæ under observation at the time in a glass jar in my verandah. Under the influence of the cold these became torpid or sluggish, and most of them seemed dead.
On the 7th, however, the sun shone out brightly, and the seemingly dead ones as well as the others became quite lively again. It is probable, therefore, that much of the diminution in numbers of the larvae in the ravines during the winter is more apparent than real, since they are most easily recognised in ordinary circumstances by their very characteristic movements when disturbed.
Dr. J. M. ATKINSON,
Principal Civil Medical Officer,
&c..
I have the honour to be,
Sir,
Your obedient Servant,
JOHN C. THOMSON, M.D)., M.A.
APPENDIX I.
PREVALENCE OF MOSQUITOES, DURING THE YEAR ENDING 30 SEPTEMBER, 1901.
Central Station,
No. 1 Station..
No. 3
No. 7
Mt. Gough,
Pokfulam, Aberdeen, Stanley, Shek 0, Shaukiwan,
Tsat Tsze Mui, Tsim Sha Tsui, Yaurati,
NAME OF STATION.
Tuk Tsun Heung,
Specimens received.
ANOPHELES.
CULEX.
Number. Species. Number. Species.
Other
Genera.
རྞྞ }།
Nil.
1,360
6
No. 2
修剪
576
1
"
1.334
1,255 574
efbikur 1,177 efbiknor
efhiku
99
I
No. 5
156
**
107
No. 6
+1
71
107 7!
chir
ebino
TAT..B.LE
"
462
447
No. 8
63
62
Kennedy Town,
eflik efhiko
15
764
716
efbiku
48
63
61
efhi
2
872
#be
831
efhikomor
20
735
b
681
efghikmur
47
980
15
ube
948
efhikuor
750
116
it
632
efhimno
1,579
1,538
eflikmoor
607
47
abe
553
efhikn
678
676
elbiku
1,069
B
1.065
efghikars
572
&
557
Stone Cutters' Island,
efhiknor
81
80
elkon
Hung Hom,.....
729
725
Kowloon City,
efhinor
1,726
a
1,716 ofhiknor
Nil.
662
43
abo
648
8
abc
Tai Po,
819
191
a be
520 544 618
efghikuops efghikn
90
96
Sha Tau Kok,. Kat 0,....
efhinnopr
4,428
414
abe
3,987
efhiknopr
10 27
709
696
Sheung Shui,
ofhi
13
$29
10
a b
906
efbikinor
14
916
14
abe
823
efhiknor
79
1,853
113
abe
1,728
efhikinnor
12
251
12
A h
283
efghikn
6
408
38
a be
361
ofhiko
9
238
78
*
148
efhikm
4,704
1
b
4,703
628
30
a be
574
efhikn efhiknor
24
Total...
32,266
1,169
abe
30.221
efghik mnoprs
876
Less,
Net Total.....
876
31,390
Sha Tin Gap,
Sha Tin,
Sai Kung,
San Tiu,
Au Tait, Ping Shan, Tai 0,-
Tung Chung, Cheung Chuu,. Lammia,
APPENDIX II.
AN ACCOUNT OF HONGKONG MOSQUITOES. A--Anopheles Sinensis (Wiedemann)."
Sub-species; Annularis.
Wings spotted. Dark brown costa, with two lighter interruptions. Dark brown spots irregularly placed on wing field. Legs brown. White-banded at joints. White bands at apices of tarsi.
Antenue and palpi brown. Proboscis darker brown. Thorax brown. Linear markings of a deeper brown. Abdomen brown, unbanded.
Length, 5 mm.
B-Anopheles Maculatus. A new species.
7
Wings spotted, transparent. Four linear black spots along costa, with three pale intervals. Also faint linear spots ou wing field at points on course of veins.
Legs black, white-banded. White bands at apices of tarsi.
Antenna grey.
Palpi black, white-banded, and white-tipped. Proboscis dark-brown, with pale tip. Thorax brown, with grey-white tomentum.
Abdomen brown, unbanded.
Length, 4 mm.
6
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