a2 MISC. PUBLICATION 336, U. S. DEPT. OF AGRICULTURE 
fact that malaria infection in this region has almost invariably been 
found associated with this species. A. crucians is prevalent along the 
coastal plains and in the lower Mississippi Valley, and since three 
specimens have been found infected in nature (120, 126), the species 
cannot be entirely eliminated from consideration. Investigations 
several years ago in the Okefenokee swamp in southern Georgia (127) 
showed that malaria was absent in an area where cruczans was preva- 
lent and the only anopheline present. In Florida the malaria rate is 
high in the northwestern part of the State, where A. guadrimaculatus 
predominates, but low in the southern half of the State, where cruczans 
is abundant and the predominating species. Such malarious foci as 
have been investigated in the southern part have shown locally favor- 
able conditions for guadrimaculatus breeding. Frequently the two 
species are found associated in the breeding places, but in general the 
occurrence of guadrimaculatus and the areas of high malaria endemic- 
ity in northern Florida and southern Georgia (25) appear to be cor- 
related with the presence of shghtly alkaline surface waters, whereas 
crucians apparently prefers water of an acid reaction as found more 
generally in the southern part of Florida. 
Barber and coworkers (10) have given a critical review of the 
records on infection of southern species and their role in malaria 
transmission. 
The species of Anopheles included here are divided into two sub- 
genera, albimanus being placed in Vyssorhynchus and the others in 
the subgenus Anopheles. King and Bradley (99, 100) have given a 
review of the classification and distribution of the Nearctic species. 
ANOPHELES QUADRIMACULATUS Say 
(Syn., A. annulimanus V. d. W.; the common malaria mosquito) 
The common malaria mosquito breeds chiefly in permanent fresh- 
water pools, ponds, and swamps that contain aquatic vegetation or 
floating debris (pls. 1-3). It is found throughout the South and is 
the principal species concerned with malaria transmission in this 
region. It isa fairly large mosquito, dark in color, with four darker 
spots near the center of the wing field (pl. 5, @). In its resting posi- 
tion the angle at which the body is held is not so pronounced as with 
some of the cther species, and the position of specimens heavy with 
blood may not appear characteristic. 
This species is active principally at night, although during the 
cooler months the females will seek blood meals in the daylight on 
warm days, in dwellings, or in the woods. The daily flight or dispersal 
period begins just at dusk and continues for a half hour or so. During 
the remainder of the night, flight is probably limited for the most part 
to local forays in search of a host. Another period of activity begins 
just at daylight and ends with a general shift to the daytime resting 
places. The flight range of Anopheles quadrimaculatus from the 
breeding places undoubtedly varies a good deal, probably depending 
largely upon the proximity of blood meals and the numbers pro- 
duced. In planning control operations the maximum effective flight 
range is taken as about 1 mile under average conditions during the 
summer. Prehibernation dispersal flights in the fall may be much 
greater than this, 
