32 MISC. PUBLICATION 336, U. S. DEPT. OF AGRICULTURE 



floating debris (pis. 1-3). It is found throughout the South and is 

 the principal species concerned with malaria transmission in this 

 region. It is a fairly large mosquito, dark in color, with four darker 

 spots near the center of the wing field (pi. 5, G) . In its resting posi- 

 tion the angle at which the body is held is not so pronounced as with 

 some of the other 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 dis- 

 persal 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 quadrimacu- 

 latus from the breeding places undoubtedly varies a good deal, prob- 

 ably depending largely upon the proximity of blood meals and the 

 numbers produced. In planning control operations the maximum 

 effective flight range is taken as about 1 mile under average condi- 

 tions during the summer. Prehibernation dispersal flights in the fall 

 may be much greater than this. 



Although little is known of the extent to which this species feeds 

 upon wild animals, man and most of the domestic animals are known 

 to be attacked by the blood-hungry females. Information on the rel- 

 ative attractiveness of different hosts was obtained in a series of cage 

 experiments conducted in Baltimore, Md. (32, 33). Two host spe- 

 cies were exposed side by side to the bites of Anopheles quadrimacu- 

 latus females, which were afterwards collected and the blood meals 

 identified by the precipitin test. Among cattle and horses it was found 

 that the attractiveness varied more between individuals than between 

 the species, and that a decided variation also occurred between indi- 

 viduals of the human race. The latter received on an average about 

 one-sixth as many bites as the horse or cow. Sheep, goats, dogs, and 

 pigs appeared to be less attractive, in the order given, while rabbits 

 and chickens proved to be very poor hosts even in the absence of 

 other animals. 



To determine the proportion of mosquitoes that obtained blood 

 meals from different hosts under natural conditions, a large series of 

 records had previously been obtained at Mound, La., (79) by testing 

 the blood from freshly fed females collected from the tenant dwell- 

 ings and outbuildings on three plantations. From a general series of 

 collections during the mosquito season of 1922, 38 percent of the speci- 

 mens taken inside the house were found to have fed on man, and 

 about 2 percent of those from underneath the house and in the out- 

 buildings. The weighted average was 4.3 percent for the entire 

 quadrimaculatus (female) population, being 6 to 8 percent when the 

 average number of females per location was about 200 to 500 and de- 

 creasing to 3 percent or less when the average reached 1,500 or more. 

 The average percentages for the other hosts for which blood tests 

 were made were as follows : Cow, 36 ; horse, 33 ; pig, 16 ; dog, 8 ; and 

 other animals (chicken and cat), 3. 



Although very high malaria infection rates (10 percent or even 

 more) have been found among anophelines in other countries, the 

 percentage of infected quadrimaculatus in malarious areas in this 



