OF THE NATIVE DOMESTIC WATER-RECEPTACLES AT LAGOS, &c. 133 
village). These facts, when considered in conjunction with the peculiar 
distribution of C. duttonz, 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 
be the carrier of this Filaria. 
Culex tigripes var. fusca, Theo. 
This species was found in an average of 5:3 per cent. of all the water- 
receptacles. As far as I have observed it is wholly carnivorus, living entirely 
upon other larvae, or on those of its own species when deprived of more suitable - 
victims. It showed preference for the larve of S. fasciata and of C. 
nigrocostalis, but in their absence, and after a little starvation, will eat the 
larve of C. duttoni and of Pectinopalpus fuscus. The presence of tigripes larvie 
in the samples of water examined has probably led to an under-estimate of the 
number of both the larve 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 larve. It showed a 
seasonal variation in numbers. 
Culex nigrocostalis, 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 
larvez 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 larvee and 
pup 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. 
20419 : D 
