August, ’20] 
ZETEK: MOSQUITO CONTROL 
345 
that the sanitary inspector is on his tour is made known long before he 
arrives. The people soon learn to fear flower vases, hence many will 
hide them so the inspector will find none. Here, also, fines are about 
the only outcome, and the result is the same as with ant-guards,—ill 
feeling toward the well-meaning sanitary corps. But, if the people 
know that there is a substance which they can place in their flower 
vases and thereby prevent calopus breeding, especially so when the 
substance will not affect the flowers, then cooperation increases and 
the sanitary inspector can do more thorough work. The days of 
actual ignorance as to the importance of yellow fever are gone; nearly 
all of Central and South America wants to clean up and get rid of this 
scourge. Hence it is believed the people will fall into line and be of real 
service in this work of eradication, especially so when all frictions 
between them and the sanitary forces are made as few and as small as 
possible. 
Other containers exist in houses. Of these the ant-guards used to 
protect tables and ice boxes from ants, are as easy to control as are the 
ant-guards in gardens. But the tinajas, or water reservoirs, are some¬ 
what difficult to handle because the people must have drinking water, 
and in tropical climates the tinajas keep this water cool. The best 
control is to substitute them with a water pipe system and a good, clean 
reservoir and such other means as will give these people good drinking 
water in sufficient abundance. Not all places can afford a first class 
water system, hence the sanitary corps must aim, by means of periodic 
inspections, to have tinajas cleaned out and kept free from yellow fever 
larvae; at any rate pupae should never be found. It is remarkable how 
much a water pipe system reduces the number of containers, and as a 
consequence calopus breeding, in houses. 
Another application of the method proposed in this paper, is in the 
urns containing holy water in the Catholic churches. These always 
will breed yellow fever mosquitoes unless some method of control is 
undertaken; it is not an infrequent sight to see the congregation 
scratching their ankles while the services are going on. 
The method proposed consists of adding small quantities of powdered 
camphor or para-dichlorobenzene to the containers. Lump camphor 
may be used in flower vases and holy water urns. Naphthalene was 
found to be unsatisfactory unless used in finely powdered form. About 
two grams per liter of water was found to be enough, but no minimum 
dose was determined because it was thought best to be on the safe side. 
Outdoor conditions, especially heat, rain and debris modify consid¬ 
erably the character of the contents of the container, hence enough of the 
chemical should be used, and two grams per liter was found to be 
satisfactory if repeated once a week during the rainy season. 
