D3091: Bumble bees of tallgrass prairies and old fields in Winneshiek County, Iowa: Survey transect length affects species richness

Bumble bees and honey bees (Hymenoptera: Apidae) provide essential ecosystem services, the most important being pollination. However, pollinator populations are declining due to factors such as habitat loss, climate change, and the use of pesticides. To gather baseline diversity and abundance data of bumble bees in Winneshiek County, Iowa, we conducted meandering transect surveys for bumble bees and honey bees at 11 different prairie and grassland sites from 3 June to 21 August 2020. We netted and collected each Bombus and Apis mellifera observed using non-lethal techniques following USFWS protocols, and identified them using keys from the University of Minnesota and Xerces Society. Twelve Bombus species were observed over the summer, including Bombus affinis, which was found at four of our 11 sites. The most abundant bees were Apis mellifera (n=361), Bombus impatiens (n=243), and Bombus bimaculatus (n=208). As the season progressed, bumble bee sightings and species richness increased. Longer survey transects at some sites yielded greater species richness of bees, as there was a strong positive correlation (r=0.81). Flowering species richness and bee species richness were also positively correlated (r=0.61). These results provide important baseline data on Bombus diversity and abundance in the prairies and grasslands of Winneshiek County.