SIGNIFICANCE OF STEGOMYIA FASCIATA IN WEST AFRICA. 255 



5. The Stegomyia in Southern Nigeria. 



In company with Drs. Pickles, Laurie and Tynan, o£ Lagos, I made a 

 thoronob house to house inspection o£ 100 houses, selected in representative 

 parts o£ Lagos^ including the poorest, lower middle class and white trading 

 classes. The houses in the poorest part of the town are veritable rat-traps, 

 dovetailed into one another, and abominably overcrowded for the amount of 

 ground space ; they are in consequence very dark, and in the course of all 

 my experiences I have never yet found so man^^ receptacles of all kinds 

 containing stagnant water, or containing such an immense number of 

 Stegomyia larvse. Altogether in the 100 houses and yards there were 489 

 collections ot* stagnant water ; these consisted of 339 earthen pots, 32 wells, 

 and the remainder of buckets, barrels, and odds and ends. Earthenware 

 pots, therefore, vastly predominated over all other water receptacles. I found 

 larvae in 252 receptacles ; and as the houses are packed closely together, lam 

 of opinion that it is understating the percentage if it is placed at 100 per cent., 

 for unquestionably each house was infested with Stegomyia^ breeding in its own 

 yard or room, or in the adjacent yard or hut. S[)eciments of adult Stegomyia 

 were present in the houses in far greater numbers than I have seen them in any 

 other part of the Tropical World. The larvae were in the vast majority of cases 

 those of Stegomyia fasciata. To make sure, however, I bred out numerous 

 batches, which were submitted to Dr. Graham, who confirmed my diagnosis, and 

 also found Culex tigripes, Cnlex lursutipalpis and Cidex albovirgatus, Graham. 

 Dr. Graham had already drawn attention to the prevalence of the Stegomyia, 

 and its danger from the point of view of yellow fever. He regards this 

 mosquito as the common species of the Coast towns. 



From the reports made by the Sanitary Inspectors and furnished to me by 

 Dr. Tynan, there is no doubt that Stegomyia fasciata is the common mosquito 

 of Lagos, and is breeding in immense numbers in that town. In the Central 

 Province of Southern Nigeria, Dr. MacDonald considers it to be the commonest 

 mosquito found breeding in water-containers. From a report furnished by the 

 Medical Officer of Sapele, the Stegomyia index in that locality is 13 per cent. 

 The Medical Officer at Warri reports that before cleaning-up operations 

 mosquito larvae were present in every compound. The Medical Officer at 

 Forcados reports the Stegomyia index as being 2 per cent. The Senior 

 Medical Officer of the Eastern Province (including Bonny and Calabar) 

 reported in July 1910 that every native house and compound contained 

 water rece[)tacles, and the larvae usually present were those of Stegomyia 

 fasciata. The Medical Officer at Opobo also draws attention in a report to 

 the universal distribution of the Stegomyia in Southern Nigeria and the 

 danger arising from this fact, were yellow fever introduced. 



In conclusion we may reasonably assume that, as in Lagos, the prevailing- 

 house mosquito of the towns in Southern Nigeria is Stegomyia fasciata. 



