Mortality of lepidoptera along roadways in Central Illinois

We conducted this study to investigate the magnitude of roadway mortality of Lepidoptera in central Illinois. To quantify the number and kinds of Lepidoptera killed along roadways, dead adult Lepidoptera were collected, identified, and counted from along 13 roadside transects in the vicinity of Champaign/Urbana, Illinois, with collections occurring weekly on each transect for six weeks. During the six weeks of this study, 1824 presumably road-killed Lepidoptera were collected. At traffic rates of 1000, 13,500, and 19,700 vehicles per day, more Lepidoptera idoptera were collected per 100 m than at other traffic rates. A peak in monarch butterfly mortality may coincide with the timing of their annual migration through the area. Based on these data, the number of Lepidoptera killed along roadways for the entire state of Illinois during one week was estimated at more than 20,000,000 individuals. The number of monarch butterflies killed may have exceeded 500,000 individuals. Our results suggest that increases in traffic rate and speed limit may to a certain extent increase mortality.