ArticLe II]—A Study of the Malarial Mosquitoes of Southern Ilh- 
nois. II. Operations of 1920.. By Stewart C, CHANDLER. 
INTRODUCTION 
The mosquito survey of southern Illinois, which was begun by the 
author in the spring of 1918, has been carried forward during the season 
of 1920 at Herrin, Williamson county, and vicinity. The object of the 
work, as fully explained in a former article of the Natural History Sur- 
vey Division,* is to locate the places which breed mosquitoes, to point out 
what types of location are especially favorable to the production of the 
malaria mosquitoes, and to increase cur knowledge of the seasonal occur- 
rence of all mosquito species to be found in southern Illinois. It is hoped 
that these articles will provide data of use to citizens of communities in- 
terested in a reduction of malarial disease through a control of the mos- 
quitoes transmitting it. It is p!anned to continue the survey, each year in 
a different locality typical of some considerable area, so that eventually 
all types will be covered. 
Before describing the work of the season, it is well to recall a few 
fundamental facts about mosquitoes and the relation between them and 
malaria. It is especially important to remember that some body of water, 
either temporary or permanent, is necessary to the development of the 
mosquito. Of the four stages through which this insect passes in its life 
cycle, egg, larva, pupa, and adult, the first three are entirely aquatic. The 
adult mosquito lays its eggs upon the surface of the water, or failing to 
find any water it may die without depositing any eggs. The common 
wigglers or wiggle-tails which hatch from these eggs pass their existence 
in the water, feeding on the minute organisms which they find there, 
until they emerge as adults, this entire process requiring from one to three 
weeks. The dependence of the malarial organism upon the mosquito 
needs no discussion here, except merely to state that malaria is transmit- 
ted to man only through the bite of certain species of mosquitoes belong- 
ing to the genus Anopheles. These mosquitoes are called the Anopheline 
or malarial mosquitoes to distinguish them from the Culicine species, 
which do not carry the disease. 
DESCRIPTION OF THE BREEDING PLACES AT HERRIN 
The situation at Herrin is typical of much of the mining territory in 
southern Illinois. The town was started at a point between three coal 
mines and has spread in all directions up to the edges of the mine prop- 
erties. Close to each mine two kinds of water are to be found, one in 
ponds cared for by the mining company and used for boilers and washers, 
* Article XI, volume 13. A Study of the Malarial Mosquitoes of Southern Illi- 
nois. I. Operations of 1918 and 1919. By Stewart C. Chandler. 
