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

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.

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