The Northern Illinois Butterfly Monitoring Network, coordinated by Doug Taron and Mel Manner, is an organization of volunteer Butterfly Monitors who count butterflies in natural areas in the Chicago region. The data, collected by Doug Taron, are used in part to monitor the quality of the natural areas and the impact of management techniques. The number of sites reporting a species is shown here in order to indicate how common or rare a species is in northeastern Illinois. The most common butterflies are found at over 20 sites, relatively uncommon butterflies in northern Illinois are found at less than 10 sites.
Have a look at the Northern
Illinois Butterfly Monitoring Network website.