Survey of the critically endangered Rusty Patched Bumble bee (Bombus affinis) at Midewin National Tallgrass Prairie, (USDA-FS) Ill.

Bumble bees (Bombus spp.) are important pollinators of many plants around the world. Recent declines in populations and range(s) of Bombus spp. are attributed to habitat loss, pesticide use and invasive pathogens. Four species have undergone notable declines in Illinois, with one, the rusty patched bumble bee (B. affinis), recently being listed as endangered under the Endangered Species Act. Prairie restoration over the past 20 years at Midewin National Tallgrass Prairie, a 20,000 acre preserve near Wilmington, IL, has resulted in much florally rich prairie habitat, yet no comprehensive survey for B. affinis has been conducted, despite known populations in several surrounding counties. In this study we recorded the presence of all bumble bee species in Midewin across 12 transects in June-August 2018. Nearly 800 bumble bees, representing a total of 9 species were recorded during this survey. B. affinis was observed just once during our transect surveys, the first known record in Will county, comprising just 0.13% of all bumble bees captured. Three other bumble bee species of conservation concern, B. vagans, B. pensylvanicus and B. fervidus were also found, representing 10% of all captured bumble bees. The results of this study show that Midewin currently supports bumble bee species of conservation concern and efforts should be made to support these populations