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(b.) Stored drinking water.—I have already pointed out that the houses in Victoria have water laid on and that the supply is usually continuous for seven months out of the twelve. It was decided to leave the search of the water storage receptacles till the intermittent system was put in force as only then is storage really necessary. When the continuous supply is in force the water tap is fixed over the storage receptacle and kept running into it more or less all the time. The result is that the receptacles are usually overflowing and the surface constantly disturbed, they do not therefore offer a very suitable breeding place for larvæ and they are very difficult to search.
During this summer there was sufficient water and the intermittent system was therefore not brought into use till very late in the season.
A search had therefore to be made with the continuous supply in force and with the following result:-
One hundred and eighty-one (181) houses were visited by me in the most densely built over area and the nature of the water storage is recorded in the following Table :-
No. STORAGE Half full Full 59 KONGS 53 16 10 WOODEN BARRELS 4 24 112 IRON TANKS 26 28 13 13When little water was present in the receptacle large scoops were used to get the specimen as far as possible from the bottom of the vessel, if the receptacle was full, the water was first disturbed to make any larvæ present go to the bottom and the bottom layers of water were pumped out and examined.
Using considerable care, only three samples of larvæ were obtained from the above 179 receptacles and in every case these were found to be stegomyia scutellaris.
As it was not possible for me to devote sufficient time to this search of the stored water, the Sanitary Department lent Inspector Millington to carry on the work.
Inspector Millington accompanied by two Chinese assistants has carried out this work very carefully and in exactly the same method as used by myself.