Examining Phenological Patterns for the Emergence Times of Common Bombus Species in the U.S. Mid and South Atlantic

The goal of this study is to examine the phenology of queen bumblebee (genus Bombus) emergence times and its connection to temperature and precipitation across the states of Virginia, West Virginia, Maryland, Delaware, and Pennsylvania. Growing degree days (GDD), cumulative precipitation (∑ppt) and days accumulated (∑day) were the metrics used to study connections between climate and emergence times. It was hypothesized the GDD for queen bee emergence times will vary between species yet remain constant within a species across latitudinal and elevational gradients, and the number of days it takes to reach this threshold will increase with elevation, latitude, and precipitation. Observations were gathered from a citizen science database and a museum database to gather current and historical trends. Data were split between high and low elevations and latitudes to compare the geographic difference in GDD and ∑day values. Results suggest that queen bee emergences currently occur most frequently in the week of March 29th-April 4th; B. bimaculatus emerges first, B. impatiens emerges second, and B. griseocollis emerges third. However, as GDD varied significantly across elevational and latitudinal gradients, temperature was not determined to be the primary factor in queen bumblebee emergence times. Phenology differences at high elevations and latitudes are not very pronounced, as emergence times only differ a couple of days between species. This suggests that day accumulation, especially at high elevations and latitudes, drives Bombus emergence times more than
temperature accumulation.