224 Annals Entomological Society of America [Vol. VIII, 
About 0.75 mile west of Gatun, this dam is cut through by a 
large spillway. Here was located a small camp (Spillway 
Camp), consisting of several labor barracks, a dispensary and 
a hotel. A mile north of this place, and nearly a mile north- 
west of Gatun, is a low, flat land, the highest portion of which 
is a small dome 20 feet high. The major portion of this region 
is below the 10 foot contour, most of it a salt-marsh. This 
region marks the early workings of the old French Canal Com- 
pany, and is bordered to the east by a deep channel known as 
the Old French Canal. The excavations of this pre-American 
attempt were dumped along the banks of this flat land. Thus 
perfect drainage was made impossible; however, the region 
never gave serious trouble to the sanitary inspector, until the 
latter part of 1912 and the beginning of 19138. At this period 
countless, in fact unbelievable, numbers of Anopheles albima- 
nus Wiede., its racial variety tarstmaculata Goeldi and Aedes 
teniorhynchus Wiede., invaded the towns of Gatun and New 
Gatun, and it was soon evident that they were breeding in this 
salt-marsh. It is this area that gave such good opportunities 
to demonstrate mosquito flight. 
East of this marsh is a low island, partly covered with a 
dense vegetation, and the rest of it composed of barren hydrau- 
lic fill. No serious breeding occurred here, however, shade 
from the hot sun was present for the mosquitos traversing the 
island. This was the main site for the LePrince experiment 
recorded in this paper. 
South of the island is a small neck of land, mostly above the 
ten foot contour, which 1s covered with luxuriant vegetation. 
This tangle of growth was cut down and burned in February, 
1913, and the measure greatly reduced the number of mos- 
quitos for the time being. 
From the breeding place to Gatun is a rise of about ninety 
feet, but east of the locks the land ranges in height from fifty 
to a hundred and fifty feet, with isolated knolls of 110 to 160 
feet. It is unusually well-drained and oiled, and it can be said 
that no Anopheles breeds within this treated area—a great 
credit to the sanitary inspector in charge, J. A. Corrigan. 
The population numbered at the time about 4,500, dis- 
tributed as follows: 800 white Americans, 1000 West Indian 
negroes, 200 East Indians, 1500 Spaniards and 1000 all others. 
