THE MOSQUITOES OF THE SOUTHEASTERN STATES 23 



Kecent work in New Jersey (48, 49, 117) has shown that outdoor 

 gatherings of people can be protected more or less from mosquito 

 annoyance by a thorough spraying of the grounds and surrounding 

 vegetation with a diluted emulsion of pyrethrum extract (similar to 

 the formula given for pyrethrum larvicide). The spray is applied 

 under sufficient pressure to produce a fine mist. Successful results 

 were reported from tests in which areas as small as 1,000 square feet 

 were sprayed, but Vannote (117) indicated that a marginal zone ap- 

 proximately 100 feet wide should be treated in addition to the area to 

 be protected. In experiments conducted in Florida by the present 

 writers (78), effective results were not obtainable with the species 

 Mansoniu perturbans on areas 106 and 150 feet in diameter (0.2 and 

 0.4 acre) when the ground was covered with only short vegetation, 

 although marked reductions had occurred from the spraying in the 

 smaller area before the grass and weeds had been cut. It was indi- 

 cated that the method would not be feasible, against this species at 

 least, for the protection of lawn parties or similar small gatherings. 



The beneficial effects of various plants or trees in repelling mos- 

 quitoes have been reported, but apparently none of the reports have 

 been substantiated when carefully investigated. (See Moznette (105) 

 for one such instance.) Different plants have also been blamed for 

 attracting mosquitoes to houses. Although no plants with such 

 properties are definitely known, it is true that dense vegetation is 

 attractive to many species of mosquitoes as a harboring place. This 

 is probably due to the moisture and shade afforded by the vegetation, 

 as well as protection from winds. Some of the woods mosquitoes are 

 also known to bite commonly in shady places during the daytime but 

 will not fly into the open for a blood meal. 



Adult mosquitoes have various natural enemies, such as certain 

 birds, bats, and predacious insects, which prey upon them along with 

 other insects. The erection of bat roosts in mosquito -infested areas 

 has been urged as a means of control, but observations in places 

 where bats are very numerous have shown that they have little effect 

 in reducing the mosquito population (64). 



SPECIFIC PROBLEMS 



A few notes are given below in regard to problems of control of 

 some of the more important species. 



THE COMMON MALARIA MOSQUITO (ANOPHELES QUADRIMACULATUS) 



This species develops principally in permanent bodies of fresh 

 water containing aquatic vegetation or floating debris (pis. 1-3). 

 Because of the breeding habits of this mosquito, malaria in the 

 Southern States is largely a disease of rural communities and small 

 towns. Malaria control in this region usually consists of measures 

 against Anopheles quadrimaculatus, the first essential of which is the 

 permanent elimination of the low swampy places by filling or drain- 

 age. This species does not ordinarily fly long distances, and the 

 control of the breeding places within a mile of a populated area is 

 thought usually to be effective (5, 1$, 86, 87). Ditches and the mar- 

 gins of the deeper ponds and lakes should be kept free of vegetation, 

 and breeding in shallow ponds full of aquatic growths or in the beds 

 of occasionally flowing streams can sometimes be controlled economi- 



