936 The Philippine Journal of Science 1915 
supply from other sources. Water equally good, even if a little 
less conveniently at hand, is found in most of these towns within 
a hundred meters or less. Again, the open sewers and other 
ditches under the houses could be cut off and only two or three 
ditches in the main streets retained. These might be cemented 
at little cost, or, if this much expense is impossible, they could 
be kept clean and their channels so arranged that the water could 
have swift and unobstructed passage and the larve could be kept 
down by the use of larvicides. Near many towns not of the 
ditched type the breeding places of Anopheles febrifer are very 
limited. In Puerto Princesa, for example, we could find but 
one such breeding place anywhere near the town. One or 
two hours’ work by one person would suffice to destroy practically 
every anopheles larva in that place. 
In localities where one or more streams flow through or near 
the houses, the destruction of the larve is more difficult, but still 
quite practicable. As a rule, the breeding places of anopheles 
do not occupy the whole margin of the brooks, but occur here and 
there where vegetation offers some protection. Cleaning out 
these breeding places would accomplish much and in many 
streams we have surveyed would require comparatively little 
time and expense. 
Permanent good may be accomplished by clearing the stream 
bed so as to make it narrower and swifter and to do away with 
some of the pools and quieter water where the larve breed. 
Work of this sort has been done successfully at the Calamba 
Sugar Estate. 
Watson 7° brought about a great diminution of the malaria 
rate in certain estates in the Federated Malay States by subsoil 
drainage of the clear streams where Anopheles maculatus breeds. 
This was done only for certain sanitary areas, and on account 
of the expense such permanent improvements would be difficult 
to carry out in most localities in the Philippines. Larvicides are 
cheaper and at the present offer a more practical method for 
mosquito destruction in these Islands. 
Since the larve of Anopheles febrifer and of other stream 
breeders have the habit of hiding in crevices in the bank and 
under vegetation, it is difficult to apply a larvicide adequately. 
However, this characteristic renders it unnecessary to treat any 
part of the stream other than the bank. Barber has made some 
experiments in the destruction of the larve of A. febrifer, the 
results of which are given in Table X. 
* Loc. cit. 
