27 
enough larvae on them to be of sanitary importance. As elsewhere, 
the fine floatage lodged with drift was the main shelter of larvae. 
Algae were a slight factor in their production at the time of the' 
survey, and doubtless a greater factor later in the season. 
This fine floatage consisted to a large extent of a small round 
granule, 1 apparently the excrement of small worms, mixed with 
detritus of wood. This material lodged against drift and, protected 
from wave action by drift or the contour of the bank, was the most 
frequent shelter of Anopheles larvas in the pond. At times there 
would be only small patches of it, or a thin layer, and at times it 
would be an inch thick. When thick it was not always easy to see 
the larvae, and many devices were used to do so. At times it would 
be compressed between pieces of drift and even forced up out of the 
water, sometimes 6 or 8 inches, high and dry. Then, of course, it 
would contain no larvae. As in other ponds, larvae were found 
most often and most" abundantly in tortuous, steep-banked bights. 
The larvae were protected from wave action by the shape of the shore, 
'while such bights usually contained drift and floatage, and small 
fish avoided the deep water close to the banks. Coles and Mayers 
bights were of this nature, the latter at one time breeding profusely. 
Sometimes a bight, or even a part of a shore line, would be pro¬ 
tected against wave action by heavy drift, and if there was even a 
small amount of floatage and the bank was steep so that minnows 
avoided it, larvae were generally found. There was such a place north 
of the mouth of Cannons Creek. 
Along the old railroad embankment a large number of larvae were 
found on two occasions on the west side, but practically none was 
found on the east. This fact was doubtless due to a southeast wind 
that usually prevailed. After a heavy squall from the southwest none 
was found on the west side. This shore was steep and had grass 
hanging over in the water with a moderate amount of floatage 
against it. 
The banks of the river were much higher than the flat lands just 
back of them, with the result that from where the banks first showed 
out of water for 2J to 8 miles higher up there were large shallow col¬ 
lections of water running behind the banks, in some places crossed by 
ridges of land and in others opening into the river through creeks 
and branches. Strange to say, we found no breeding of sanitary im¬ 
portance in these places. Occasionally, a number of larvae would be 
found in bulrushes or about the mouths of creeks where drift and 
floatage had collected, but we did not find these wide sloughs produc¬ 
ing. They were alive with minnows. Nor did we find much breeding 
in the bayous of creeks. 2 
1 It was best seen with a hand lens. 
2 We dipped both from 'the banks and from canoes. 
