140 
MALARIA 
which are not flushed away by floods, their 
water is acid and deters A. quadrimaculatus 
propagation. This applies also to similar 
areas in South Carolina and Florida. Solu¬ 
tion topography is not encountered to any 
great extent in these coastal low lands. 
Malaria in the southern states adjacent to 
the Mississippi River is likewise not asso¬ 
ciated to any great extent with limesink or 
solution topography. In this region the 
malarious districts center around one or 
more large river systems, and occur espe¬ 
cially along the flat alluvial valleys and 
fluvial swamps which follow the broad bed 
of the Mississippi. The whole western bor¬ 
der of Tennessee is subject to overflow, and 
the valleys of tributaries adjacent to the 
master stream may be flooded several times 
during the year. Meleney, Bishop and Rob¬ 
erts (1929) point out that malaria in west¬ 
ern Tennessee is confined essentially to these 
flood plains, and as such is a part of the 
malaria problem of the entire Mississippi 
delta. In eastern Arkansas, southeastern 
Missouri, Mississippi, and Louisiana highly 
endemic malarious regions are centered 
along the St. Francis, White, Arkansas, 
Ouachita, Red, Yazoo, and Mississippi Riv¬ 
ers. The broad alluvial plain between the 
Yazoo and Mississippi Rivers is responsible 
for a large part of the malaria in Mississippi 
(Barber and Komp 1929c). Numerous 
creeks and tributary streams of this region 
are sluggish and turbid during most of the 
year and “ox-bows” are commonly formed 
as described previously. Wooded swamps 
and spring-fed ponds also occur along the 
eastern border of the delta, and these pro¬ 
vide breeding places for A. quadrimaculatus. 
Fertile valleys in the eastern and south¬ 
eastern ^arts of Oklahoma, drained chiefly 
by the Arkansas River, include most of the 
malarious counties of this state, and the 
endemic' centers in Texas are situated 
chiefly around the Rio Grande, Red and 
Sabine Rivers. 
In southwestern Kentucky relatively mi¬ 
nor endemic foci are found associated with 
the Ohio, Mississippi, Tennessee, Cumber¬ 
land, and Blood Rivers. 
Along the upper Mississippi and Missouri 
Rivers endemic foci or sporadic outbreaks 
of malaria have been reported recently, 
which are associated in part with im¬ 
pounded water projects to provide better 
navigation facilities and for flood control. 
In the glaciated region north of the Ohio 
River, lakes, ponds, swamps and marshes 
occur that were formerly associated with 
malaria. The fact that this region is no 
longer malarious is due more to its social 
and economic development than to the ab¬ 
sence of places for A. quadrimaculatus 
propagation. 
Most of the situations referred to pre¬ 
viously are confined to sea-level or near 
sea-level elevations, and the vector is A. 
quadrimaculatus. Quite a different topo¬ 
graphical picture, however, from any so far 
described is found in the malarious districts 
of New Mexico and California. Barber and 
Forbrich (1933) define three widely sepa¬ 
rated regions of endemic malaria in New 
Mexico. The first occurs in the valley of 
the San Juan River near Farmington, at an 
elevation of 5300 feet. Here A. maculi- 
pennis breeds in large areas of swampy 
meadows and is considered to be the impor¬ 
tant vector, although A. pseudopuncti- 
pennis is also present. A second malarious 
district is located in Rio Grande Valley, in 
the vicinity of Espanola, at an elevation of 
5600 feet. The third district is located in 
the southern part of the state near Las 
Cruces, at 3800 feet, in which drainage 
ditches and irrigation canals are the breed¬ 
ing places. Malaria in New Mexico, then, 
is associated with high elevations, irrigated 
river valleys, and the presence of A. maculi- 
pennis, a distinctly different epidemiolog¬ 
ical picture from that of the Gulf and At¬ 
lantic Coastal Plains. 
In California malaria is transmitted by 
A. maculipennis and has always occurred 
principally in the San Joaquin and Sacra¬ 
mento River valleys which lie between the 
coastal mountain ranges and the Sierras. 
The San Joaquin flows northward, the 
Sacramento southward, and they join each 
other near the coast to empty into San Fran¬ 
cisco Bay. In former times the vector found 
breeding places in fluvial marshes of the 
