ArTIcLe XI.—A Study of the Malarial Mosquitoes of Southern Illi- 
nois. I. Operations of 1918 and 1919. By STEWART C. CHANDLER. 
INTRODUCTION 
The Relation of Mosquitoes to Malaria—The part which mosquitoes 
play in the transmission of malaria was established years ago, but we often 
find people who never heard of the relation between the two. It is there- 
fore important to make clear, at the beginning of this report on mosqui- 
toes, the facts in the case. Malaria was at first thought to be carried to 
men by damp night air. “Mal-aria,” bad air, was the name given to the 
disease for that reason. It was later clearly established that mosquitoes 
breeding in the swamps and other damp places and biting at dusk are 
the sole carriers of the disease. A mosquito, upon biting a malaria pa- 
tient in whom the disease parasites have developed for about ten days, 
sucks up the parasites into her mouth. Only the female mosquito bites 
and is capable of transmitting the disease. The germs now develop for 
a period of eight to ten days. In this time they break through the lining 
of the stomach wall and get into the salivary glands, from which they are 
readily transferred to man by the bite of the mosquito. Not all kinds 
of mosquitoes are malaria carriers. Only three species in this country 
(all belonging to the genus Anopheles) are implicated. There are in all 
twenty-four species of mosquitoes regional in Illinois. 
Malaria in Southern Illinois—Illinois is not usually regarded as a 
state in which. malaria is common; and the northern two-thirds would 
not be so classed. Southern Illinois, however, has a reputation not so 
enviable. I have found it impossible to secure correct statistics on the 
extent of malarial disease. Most physicians whom I have consulted do 
not keep records of malaria such that they can say definitely how many 
cases they have treated in a year’s time. They report irregularly or not 
at all on this disease to the State Board of Health. Estimates, of course, 
can be secured from them, and I have always found physicians whom 
I have consulted very willing to make as careful estimates as possible. 
Taking as examples the two towns in which I have done most of my sur- 
vey work, Carbondale and Murphysboro, I found that the estimates gave 
Carbondale from a hundred and fifty to two hundred cases of malaria 
in an average year, and Murphysboro from two hundred to four hun- 
dred cases. As these are towns of six and eight thousand population, 
respectively, we find that from two to five out of every hundred men, 
women, and children are attacked by malaria each year. There are many 
other points in southern Illinois, especially along the Mississippi, Wabash, 
and Ohio rivers, which are greater malaria centers than the towns men- 
