IN EACH HOUSE 71 



contains can generally be roughly estimated by look- 

 ing through the open door. One litre of mixed oil to 

 every square metre of water surface is the measure 

 allowed ; it need not be exact. The oil must be 

 poured in from the litre measure, and then the water 

 in the cesspool well stirred with the broomstick to 

 ensure that the oil spreads evenly. If the cesspool 

 cannot be found, but is known to exist, some oil 

 should be poured into each water-closet and sink. 

 This will pass with the seal-water into the cesspool, 

 and spread over its surface ; but this method is not 

 so efficacious as actually opening the cesspool itself. 

 The householder should then be invited to see that 

 all water collections in the house are emptied on that 

 day every week regularly. All flower vases, jugs, 

 basins, buckets, saucers, or anything that contains 

 water must be dried out. 



If the water cisterns on the roof are exposed to 

 the hot sun, or if they contain only filtered water, 

 there will be no mosquito larvae in them probably, 

 and they may then be ignored. But if these conditions 

 are not present, and mosquitos are found breeding in 

 house cisterns or water tanks, it is better to cover 

 them with a fine-mesh galvanised-iron wire net. In 

 some towns the only mosquitos found breeding in 

 such cisterns are the harmless Theobaldia spathipalpis, 

 which do not suck blood. (This observation applies 

 to the Mediterranean littoral only.) Turn on the water 

 in the bathroom and see if any mosquito larvae or 

 pupae are in it, and act accordingly. Lastly, warn 

 the householder to look out for dirty water in the 



