^ ■ 
of or stored in tight metal containers until col- 
lected. Rabbit hutches and other animal pens con- 
tribute to the fly population unless they are cleaned 
frequently. Again, the droppings should be stored 
in tight containers until collected. 
Any objects that might accumulate and hold 
water should be removed or inverted to prevent 
mosquito breeding. Water in bird baths should be 
changed twice weekly. Lily and fish ponds should 
be treated chemically or stocked with top 
minnows. Gutters along roofs of houses and other 
buildings should be kept free of leaves and twigs 
so that they drain completely. Underground drains 
for the removal of water from downspouts should 
not be allowed to clog. 
Catch basins of municipal storm sewers consti- 
tute an important source of mosquitoes in many 
urban areas. For example, many of the Culex mos- 
quitoes thought to be involved in the transmission 
of the virus causing the outbreak of St. Louis 
Encephalitis in Louisville, Kentucky, in 1956 
probably developed in the thousands of catch 
basins throughout the city. Where storm sewers 
and sanitary sewers are combined, catch basins 
with water traps at the inlets are needed to prevent 
the escape of obnoxious odors from the sewer. 
However, there appears to be little need for catch 
basins in inlets of separate storm sewers, espe- 
cially in communities with well paved streets. The 
inlets to separate storm sewers may be constructed 
35 
