132 W. M. GRAHAM — RESULTS OBTAINED FROM A MONTHLY EXAMINATION 



has been used for washing clothes, &c. It is very frequently associated with 

 S.fasciata in the same vessel and, like it, is found in both pots and barrels. It is 

 commonest in pots, probably because the foulest water is usually found in these 

 vessels. Early in the investigation my attention was aroused by the strange 

 frequency with which this larva occurred, for it seemed improbable that the 

 mosquito of the second commonest larva of Lagos shoidd have remained 

 unrecognised by previous observers, and should have continued since 1907 to be 

 represented by a few males collected in Ashanti. As the insect evidently 

 belonged to the genus Culiciomyia, from which it has been separated on account 

 of the peculiar scales on the male palpi, I determined to examine the types of 

 that genus at the British Museum when I reached London. 



On doing so I found that the scales on the male palpi of Pectinopalpus were not 

 peculiar to that genus. A detailed examination of the male genitalia of both 

 genera would be desirable, but in its absence it seems to me that Pectinopalpus 

 fuscn.i, Theo., is likely to prove a synonym of Culiciomyia freetownensis, Theo. 

 This larva showed monthly variation in numbers and appeared to be commoner 

 at Lagos than at Ebute Metta. 



Culex duttoni, Theo. 



The larva of this mosquito occurred in an avei-age of 8"3 per cent, of the total 

 receptacles examined. Its distribution is apparently greatly influenced by 

 environment. As shown in the tables, it is rare in Lagos, but at Ebute 

 Metta it is the commonest larva with an average of 78'4 per cent. Seeking 

 an explanation of this difference in distribution, an analysis was made of three 

 samples of water received from Lagos receptacles which did not contain this 

 larva, and of the three samples from Ebute Metta water-receptacles in which 

 the larva had been found, with the results shown below : — - 





Lacos. 





Erute Metta. 



1. Chlorine 



... 2-4 parts per 100,000 



1. Chlorine 



... 1-4 parts per 100,000 



2. 



... 3-6 



2. 



... 1-4 



3. 



... 15-0 



3. 



... 1-8 



Apparently then this species prefers water containing only a small amount of 

 chlorine, and is sensitive to any great variation in its amount. It also shows a 

 seasonal variation in numbers. 



During the progress of this investigation three native patients suffering from 

 Calabar swelling were sent to the laboratory for the purposes of diagnosis. 

 Filaria diurna was readily found in the peripheral blood, and all three natives 

 lived on the mainland (two at Ebute Metta and one at Agage, an adjacent 



