Nature Bulletin No. 20   June 23, 1945
Forest Preserve District of Cook County
Clayton F. Smith, President
Roberts Mann, Superintendent of Conservation

****:MORE ABOUT MOSQUITOES

Twenty-two species of mosquitoes are found in large numbers in Cook 
County. One species lays its eggs in water collected in hollow trees and 
logs. The other twenty-one species are classified in four groups 
according to their breeding habits.

There are five species of the "woodland" group. These lay their eggs in 
little depressions in the woods, to be hatched after the warm rains in 
April or May of the following spring. They are all large, showy 
mosquitoes but have a short flight range.

The "marsh" mosquitoes, of which we have six species, lay their eggs in 
the bottomlands and temporary swamps. These may fly as far as fifteen 
miles from their breeding places.

The third group breeds in permanent lakes, ponds and marshes, and also 
in polluted streams. They have also a long flight range. We have six 
species of these most common, including two species of the Anopheles 
which transmit malaria, and two species which do not bite humans. The 
females of the "nonbiters" get their required blood by biting the heads 
of birds .

Finally, we have four common species of "domestic" mosquitoes which 
hibernate over the winter in basements and such protected places, 
sallying forth in the spring to lay their eggs in every conceivable place 
where water collects. Their principal breeding places are in polluted 
waters, but they also breed in old tin cans, clogged roof gutters, bird 
baths, cisterns, catch basins and basement floor drains. Weeds, 
shrubbery and tall grass do not breed mosquitoes, but they do harbor 
them during the heat of the day.