THE MOSQUITOES OF THE SOUTHEASTERN STATES 15 



If the work is undertaken for the control of one of the common 

 diseases, such as malaria or dengue fever, the presence of the disease 

 itself, in the Southern States at least, indicates a particular species of 

 mosquito. A study of the distribution of human cases of the disease 

 serves to localize the problem, and a mosquito survey is undertaken 

 to aid in developing the plan of procedure. At the same time the 

 possibilities of including control measures against purely obnoxious 

 species that may be present should not be overlooked. Where relief 

 from annoyance is the main object, a thorough species survey is 

 necessary to determine what the problem is and the relative impor- 

 tance of the different kinds, since more than one species is usually 

 involved. Even in coastal areas, where it is known that the salt- 

 marsh species are the principal culprits, it is still highly important 

 to know whether fresh-water breeders are sufficiently numerous to 

 require consideration. 



The surveys are begun by the collection and identification of both 

 adult and larval specimens. During an outbreak of mosquitoes the 

 species involved can be determined quickly by collecting adults from 

 various parts of the affected area. In localities where mosquitoes are 

 present more or less continuously, or where outbreaks are of frequent 

 recurrence, collections should be repeated often enough for the relative 

 annual abundance of the different species to be determined. At the 

 same time information should be accumulated as to the breeding 

 places of the common species, the topography of the area, and the 

 extent of the control problem. A year should ordinarily be regarded 

 as the minimum time for such preliminary studies, since mosquito 

 abundance varies greatly with the seasons. Several years are re- 

 quired to obtain reliable averages as to normal abundance. Although 

 control operations usually can be begun before such an extensive 

 survey is completed, the practice of beginning such work with in- 

 adequate information is highly wasteful and may result in complete 

 loss of public confidence in a worth-while project and possibly cause 

 its abandonment. An important item in the annual budget for 

 financing the control operations should be the provision for con- 

 tinuing the systematic collection and identification of specimens. 

 This will furnish invaluable information as to seasonal changes in 

 the mosquito problem and outbreaks from overlooked or distant 

 breeding areas, and is indispensable in measuring the results 

 accomplished. 



General methods of collecting mosquitoes have been discussed in 

 a preceding section. Some of the special methods employed for 

 obtaining data necessary in connection with surveys and control op- 

 erations are described in the following paragraphs. 



BITING RECORDS 



Collecting mosquitoes while they are biting is the simplest and most 

 direct method of determining the proportions of the different blood- 

 sucking species. Such collections are usually made with a chloro- 

 form tube or other type of killing bottle. For data on comparative 

 abundance in different parts of the area or at different times of the 

 year, stations are selected and collections made for equal periods and 

 under conditions as nearly uniform as possible. In obtaining such 

 records the writers have adopted the procedure of sitting on a box or 



