24 MISC. PUBLICATION 336, U. S. DEPT. OF AGRICULTURE 
anopheline larvae because of their habit of feeding at the surface and 
ingesting all small particles that he on the surface film. It is effective 
in such minute quantities that its use on ground waters is not danger- 
ous to animals. One to ten percent of paris green is used with an 
inert diluent such as fine road dust, hydrated lime, pulverized soap- 
stone, or other available earths. It is applied with various types of 
hand dusters or, for larger operations, with power dusters mounted in 
boats. Tests on the use of airplanes for treating large breeding areas 
were first carried out by the writers in 1923 and 1924 (96, 97), and this 
method has since been employed in practical control operations (42, 
90, 148, 150). In airplane dusting the proportion of paris green is in- 
creased to 10 to 50 percent. The applications of both arsenicals and 
light oils must be repeated at about weekly intervals throughout the 
breeding season, since these materials remain effective for only a short 
period. : 
An adult anopheline density index (92), obtained by periodic counts 
of the numbers present in favorable daytime resting places (inside 
and underneath dwellings, in stables, outhouses, etc.), is highly useful 
in measuring the effectiveness of the control operations. 
THE DOMESTIC MOSQUITOES (AEDES AEGYPTI AND CULEX 
QUINQUEFASCIATUS ) 
Urban antimosquito campaigns usually combine control measures 
against the yellow-fever and the southern house mosquitoes, and, 
although their practical control offers no unsurmountable difficul- 
ties, continuous efforts and expense are required to keep the num- 
bers reduced. These species differ in breeding habits, especially as 
regards polluted waters and ground pools, although rain barrels and 
similar water containers are important breeding places for both. 
Where the water in these receptacles is required for domestic purposes, 
the barrels should be kept tightly covered and the water drawn from 
a spigot at the bottom; otherwise they require weekly emptying or 
treatment with oil, either of which is likely to be neglected. When 
larvae are present, spraying the surface with a small amount of kero- 
sene or a pyrethrum fly spray is effective and imparts little odor to 
the water. Fire barrels may be treated by adding borax or common 
salt at the rate of 4 or 5 pounds per 50 gallons of water. This will 
prevent larval development as long as the strength of the solution 
is maintained. ‘Tubs and other casual water containers left in the 
yard should be turned upside down when not in use, and worn-out 
equipment should be disposed of. 
With the yellow-fever mosquito (Aedes aegypti) the smaller water 
containers, such as old cans, bottles, flower vases, and obstructed eave 
troughs, are important, and a campaign against this species should 
begin with a clean-up of yards and vacant lots. During the dengue- 
fever control work in Florida in 1934 a large proportion of the dis- 
carded automobile casings left in the open were found to contain 
water with aegypti larvae, and many breeding places were found in 
automobile-wrecking yards. Toilet bowls and flush tanks in vacant 
houses and apartments require systematic attention, and collections 
of water in the basements of buildings should not be overlooked. The 
adults of this species do not fly far, and when they become trouble- 
