162 J. W. SCOTT MACFIE AND A. INGRAM. 



During the twelve months selected for this investigation (December 1914 to 

 November 1915), 417 samples containing mosquito larvae were submitted for 

 examination (see Table I). For the first seven months a considerable number of 

 samples were received monthly, but in July the numbers fell off abruptly and during 

 the last three months very few indeed were submitted. Several causes may have 

 contributed to bring this about. At the beginning of the investigation the co- 

 operation of the Medical Officer of Health was obtained and he very kindly promised 

 to send us as many samples as possible. This no doubt led to a stimulation of the 

 Inspectors and consequently to an increase in the number of prosecutions, and as the 

 fine imposed for harbouring mosquito larvae is a considerable one to the native, it 

 probably brought about a greater care on the part of householders in the course of a 

 month or two. The fact that we were away on leave from August until December 

 may also have had a bearing on the case, as it may have been supposed that the 

 maximum number of samples was no longer desired. On the other hand the falling 

 off in the numbers might have been due to a seasonal variation in the incidence of the 

 mosquitos themselves, but for the reasons stated later on we consider this to be 

 improbable. 



The Species of Mosquito Larvae Identified. 



Ten different species of mosquitos were found in the 417 samples, namely, one 

 Anophehne, four Stegomyias, and five other Cuhcines. Steyomyia fasciata was found 

 in 373 of the samples (88'44 per cent.), Culexfatigans in 62 (14*86 per cent.), Anopheles 

 cosfcdis in 4 (0'95 per cent.), Culex decens and Cidiciomyia nebidosa each in three 

 (0'71 per cent,), Stegomyia luteocephala and Stegomyia metallica each in two (0*47 per 

 cent.), and Culex invidiosus, Culex tigripes ya,T.fusca, and Stegomyia unilineata each 

 in one (0'23 per cent.). It is evident therefore that there Avere only two species that 

 could be said to be common domestic mosquitos, namely Stegomyia fasciata and Cidex 

 fatigans, and that of these two the former preponderated. 



Only six of the 417 samples were from Victoriaborg ; all the rest were from native 

 compounds. In the samples from Victoriaborg, however, six species were found, 

 namely, Stegomyia fasciata and Cidiciomyia nehulosa each thrice, Stegomyia luteo- 

 cephala twice, and Culexfatigans, Stegomyia ?nefallica and Stegomyia unilineata each 

 once. Thus only seven species were foimd in the native compomids, namely. 

 Anopheles costalis, Culex decens, C. fatigans, C. invidiosus, C. tigripes var. fusca, 

 Stegomyia fasciata and S. metallica. 



In 1,043 samples from the native compounds at Lagos Graham found six different 

 species — Stegomyia fasciata in 92"5 per cent., [Pectinopalpus fuscus) Culiciomyia 

 nehulosa in 21 "6 per cent., Culex duttoni in 8"3 per cent., Culex tigripes var. fusca in 

 5"3 per cent., and (Culex nigrocosfalis) C. decens and [Pyretophorus costalis) Anopheles 

 costalis each in 1*8 per cent. It is interesting to contrast these results with those 

 obtained at Accra. In the native compoimds of both towns Stegomyia fasciata is by 

 far the most common species. The only other species that was at all common at 

 Accra, Culexfatigans, was not found at Lagos in a single sample ; and Culiciomyia 

 nehulosa which came second in Graham's list was not found in the native compounds 

 of Accra although it was found thrice in Victoriaborg. The four species common to 

 the two lists are Anopheles costalis, Cidex decens, Culex tigripes var./wsca and Stegomyia 

 fasciata (see Table II.). 



