x, B,3 Barber et al.: Malaria in the Philippines 189 
Owing to the proximity of a high range of mountains the 
region is well watered. A large river with numerous bayous 
flows through the colony grounds, and the region is well supplied 
with brooks of clear water. 
A large part of the land is devoted to coconut trees, but 
there are some irrigated rice fields. Larvee of Anopheles rossi, 
A. febrifer, and A. barbirostris were found in the river and in 
various brooks in the colony. 
The time at our disposal at Iwahig was too short to organize 
an effective corps of mosquito catchers, so all imagoes caught 
were obtained inside of sleeping nets. These nets, where used 
by the prisoners, were often badly adjusted, and mosquitoes could 
enter under the edges or from beneath where the sleeping mats 
failed to cover the floor or the bottoms of the bunks. The record 
of mosquitoes caught is given in Table III. Here both the 
anopheles of different species and, under the head of ‘‘Culex,’- 
mosquitoes not anopheles are included. Dates of catches are 
given, different buildings are noted, and in one column only the 
mosquitoes caught in a certain bed are included. On certain 
mornings the bed nets were left down so as to facilitate the 
capture of mosquitoes. Each bed was occupied by only one 
person. 
The houses on the river bank are from 5 to 7 meters above 
the large river noted above in which larve of A. febrifer, A. 
rossu, and A. barbirostris were found. The brigade dormitory 
is a large building separated from the houses on the river bank 
by a nearly open parade ground approximately 160 paces broad. 
A careful search, continued through several days, showed that 
there was at that time no mosquito breeding place nearer the 
brigade dormitory than the river. So the distance of flight to 
this dormitory must have been at least 170 paces. In accounting 
for the fewness of mosquitoes in the brigade dormitory, there 
must be taken into account not only the distance of flight, but 
also the fact that mosquitoes in coming from the river are 
naturally first attracted to the houses along the river bank. 
Again, the brigade dormitory is partially inclosed, and the beds 
occupy three stories. On the third floor of this building 39 nets 
at one collection yielded only 7 specimens of culex and none of 
anopheles. The beds in the houses on the river bank, on the 
other hand, were on the veranda, a little above the ground level. 
Balsahan and Esperanza are small barrios of the colony. The 
beds are in small dormitories but little above the ground level 
and only a few rods from brooks where larve of A. febrifer 
were found. 
