Report on Mosquitoes Collected in St. Louis County During 1942 41 
ably to be found in the fact that Acdcs prefer small, temporary 
and inconspicuous collections of water, and occur in tree holes. 
T 
The figures may give a slightly erroneous impression of the 
abundance of Anopheles quadrlmaculatus, because, at least in 
the Jeflferson Barracks area, malaria carrying mosquitoes were 
particularly studied. 
tip 
ety of breeding places than any other species. In addition (see 
Table 6) it has been found in association with 11 other species, 
more than any other. A. quadrlmacidaUis on the other hand is 
more restricted in its breeding habits than any species which has 
been found so frequentl}'. Nearly 80 per cent of A. qttadrima- 
culatus larvae are found in ponds. After ponds, ditches and 
streams produce more mosquitoes than any other of the 16 listed 
breeding places. Actually as far as numbers of mosquitoes are 
concerned catch basins must be of great importance, for larvae 
of C. pipiens and C. restuans may be found there in enormous 
numbers. 
\ 
In rural parts of the county open sewage ditches probably 
produce more actual nuisances by the mosquitoes they breed than 
any other source. We have found such collections of water to be 
literally black wath larvae. If the suggestion of Casey and Broun 
(1938) that there is a correlation between small streams and 
open sewers and cases of St. Louis encephalitis in the 1933 epi^ 
demic, and if C. pipiens is shown to be a vector in nature as wel 
as in the laboratory, then such places become a real health hazard 
in addition to being a public nuisance. The only method of deal- 
ing with such a breeding place is the installation ot a proper 
method for sewage disposal. In fact, it will be seen that the va^t 
- majority of the mosquito breeding places in the county are man 
made, or maintained by man. The remainder, such as swamps, 
streams and lakes could be drained, or treated without undue 
difficulty. 
