THE DOMESTIC MOSQUITOS OF ACCRA. 173 



Only five species are common to tlie two lists, namely, Atiopheles costalis, Culex decens, 

 C.fatigans, C. invidiosus, and Stegomyiafasciata, and whereas Mansonioides africanus 

 and M. uniformis, by far the commonest mosqiiitos in the bungalow, do not figure at 

 all among the larvae, Stegomijia fasciata which heads the list of larvae is last on the 

 list of mosquitos. 



There were of course good reasons for these differences, some of which it was not 

 difficult to ascertain. The bungalow in which the mosquitos were caught was 

 situated in the European quarter, and no mosquitos were allowed to breed in the 

 compound. There can be little doubt indeed that the considerable numbers of 

 mosquitos usually to be found in this house must have come from a distance, as there 

 was no place in the immediate vicinity where they could have been bred. But 

 Mansonioides africanus, for example, is known to have a considerable range of flight, 

 and as it breeds in pools in association with the water-weed Pistia slratiotes, it is 

 natural that its larvae were never received in the samples collected in the compounds. 



It is not easy to account for the rarity of Stegomyia fasciata in the bungalow. 

 This mosquito, the house-haunting mosquito par excellence, which breeds in domestic 

 water-vessels and is known to require feeds of blood for the maturation of its eggs, 

 one would naturally expect to figure largely in any collections made in human 

 habitations at Accra. In a bungalow in the European quarter, however, where every 

 precaution is taken to prevent the breeding of mosquitos its absence might be 

 explained, since it is said not to fly far, and in any case a long flight in search of blood 

 must seldom be necessary for it. But recently a number (156) of mosquitos have 

 been collected for us in a native's house in block xvii. of Accra, a locality in which 

 Stegomyia fasciata abounds (see Table V. and Maps), and yet not a single specimen 

 of this species has been caught up to the present.* It is possible that Stegomyia 

 fasciata may prefer to bite in the open and may be disinchned actually to enter 

 dwellings, but the occurrence of this mosquito in houses in large numbers has 

 repeatedly been recorded by others, and one of us, in the Gold Coast, has frequently 

 taken it in Europeans' bungalows in Ashanti and the Northern Territories, but 

 usually in the afternoon between 3 and 6 p.m., and not at night. A more probable 

 explanation of the facts recorded above is therefore that Stegomyia fasciata, whilst 

 entering houses to obtain feeds of blood, does not roost indoors. 



A consideration of the two lists shown in Table VI. convinces us that an examination 

 of the larvae found in the compounds not only fails to give any adequate idea of the 

 mosquito fauna of a town, but also fails to indicate the species of mosquitos to the 

 attacks of which the inmates of the houses are liable. It also furnishes proof of the 

 necessity for extending anti-mosquito measures so as to reach the species that breed 

 far afield. 



A Note on the Distribution of certain of the commoner Mosquitos found on the 

 West Coast of Africa. 



It is not easy to state what are the exact natural conditions which determine the 

 presence of a particular species of mosquito in one locality and its absence from 

 another. An adequate supply of food for the growing larva is generally regarded 



*The mosquitos referred to have been identified as follows : — Anopheles costalis, Culex 



fatigniis and Mansonioides africauus. 



