Butterflies (such as the Swallowtail to the left) are generally distinguished from moths (such as the Polyphemus below) by their knobbed antennae. Moths have narrow or feathery antennae. Both of these insects are common in the Midwest.

The Illinois State Insect, the Monarch butterfly, passes through this area in summer as it migrates to Mexico. On their way north, the Monarchs often breed in the Chicago area.