OF THE NATIVE DOMESTIC WATER-KECEPTACLES AT LAGOS, &C. 133 



village). These facts, when coosiderecl m conjunction with the peculiar 

 distribution of C. duttoiii, its sensitiveness to environment making it common in 

 some localities and uncommon in others, the fact that it feeds during the daylight, 

 and that it is a domestic mosquito, make it appear possible that this species may 

 he the carrier of this Filaria. 



Culex tigripes var. fusca, Theo. 



This species was found in an avei'age of 5*3 per cent, of all the water- 

 rece2:)tacles. As far as I have observed it is wholly carnivorus, living entirely 

 upon other larvffi, or on those of its own species when deprived of more suitable 

 victims. It showed preference for the larvte of S. fasciata and of C. 

 nir/focogtalis, but in their absence, and after a little starvation, will eat the 

 larvre of C. duttoni and of Pectinopaljius fuscus. The presence of tigripes. larvaj 

 in the samples of water examined has probably led to an under-estimate of the 

 number oE both the larvas it prefers, as several hours always elapsed between 

 the collection of the samples and their examination at the Laboratory. This 

 larva is the chief natural enemy of domestic mosquito larvse. It showed a 

 seasonal variation in numbers. 



Culex nigroeostalis, Theo. 



This larva was present in an average of 1*8 per cent, of the total water- 

 receptacles. It is a small, delicate, long-syphoned larva, easily injured by 

 change of normal environment. As it is a favourite food of C. tigripes, its 

 occurrence has very probably been under-estimated. It shows seasonal variation 

 in numbers and appears to be commoner at Ebute Metta than at Lagos. 



Pyretophorus costalis, Loew. 



The larva of this species was found in an average of 1'8 per cent, of all the 

 water-receptacles examined. It has become almost an axiom that Anopheline 

 larvfe need only be sought in pools and puddles, or other natural collections of water. 

 The discovery that P. costalis breeds habitually in the domestic pots and barrels 

 of native yards is therefore of some importance. Of 1,043 water-vessels 

 examined in eight months 19 were found to contain this larva. Both larvte and 

 pupje were found and were successfully reared in the Laboratory, so that it is 

 likely they also reached maturity when left undisturbed in native yards. 



From the tables it will be seen that on an average 2 per cent, of the vessels in 

 Lagos harboured this larva, and that in the month of February, 1911, this 

 average rose to 6*3 per cent. Possibly this rise was caused by the absence of 

 suitable puddles or pools at the end of the dry season. The species was not 

 found in the samples of water from Ebute Metta, but as only 87 such samples 

 were received the possible existence of at least 1"0 per cent, would not be 

 excluded. 



