D3069: Bumble bees of Rhode Island: Relative abundance, diversity, and floral visitation

Bumble bees (Bombus spp.) are experiencing worldwide declines due to parasites, pesticides, competition, habitat loss, and climate change. To assess the status of bumble bee species in Rhode Island, I conducted a statewide survey using passive and active sampling methods. Bumble bees were collected using blue vane traps at farms, golf courses, and in residential areas throughout the state from May through September in 2019-2021. Floral transect surveys were also performed in 2020 and 2021 at gardens, nature preserves, management areas, and other private-owned lands with abundant floral resources. Bees were temporarily captured and identified in the field, and the forage plant of each bee was recorded. Species data from other bee studies conducted in Rhode Island within the past ten years were added to modern species records. The relative abundance and diversity of bumble bee species in modern bee surveys was compared to historical specimen records from Rhode Island. Historical floral visitation of local bumble bee species was determined by analyzing pollen samples from 70–120-year-old specimens. Our results indicate that only seven of the original eleven bumble bee species known from Rhode Island were observed in modern surveys. Bombus impatiens was observed most frequently, while Bombus fervidus was rarely observed. Bumble bee species diversity was highest on red and white clovers, and butterfly milkweed. The results of this survey will provide improved planting recommendations for increased bumble bee floral resources.